Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

Hi Pierz,

On 21 Jun 2017, at 15:31, Pierz wrote:

Bruno, do you believe there is a different world for every possible  
basis in which a spin (or other observable) might be measured? That  
seems pretty strange.





I believe in 0 worlds, but in many relative computational histories,  
in arithmetic. Linearity at the bottom ensures that the experiences  
will not depend on the basis chosen for the "universe", but the  
stories guides the consciousness flux, say, toward  stable sharable  
and hopefully sustainable realilties.
Do those dreams cohere enough to define well determined physical  
world? That is just a complex question which would need some progress  
in the definition of what could be a physical world.


For QM, I use a multi-multiverse, choosing a base, is choosing a  
multiverse, (I have called that a partition of the multiverse, also).  
Wallace things similar, I think, but I would say it literally follow  
from how Everett explains it it seems to me; notably where he explains  
the base independence of the many realities.
The global system has no "well defined " subsystems, but the sub- 
systems themsemselve beg to disagree on this, and can locally see  
themselves as part of some subsystem of a larger system.


Keep in mind I do not assume QM in physics, but digital mechanism in  
the "mind science".


The wave seems to work, and the question is where do that wave come  
from? I suspect already the prime numbers, but there is is only one  
way that I know to get both the quanta and the qualia, which is the  
"interview of the (Löbian-Gödelian) machine (using Solovay G/G*  
theorem).


If the prime numbers are "guilty", then I guess RH is undecidable in  
PA (and thus true, as even RA can refute RH if RH is false!). Maybe  
the metamathematics could recover the qualia from this, I don't know.


Bruno







On Wednesday, June 21, 2017 at 10:27:14 PM UTC+10, Bruno Marchal  
wrote:

On 20 Jun 2017, at 19:44, Brent Meeker wrote:




On 6/19/2017 11:47 PM, Bruno Marchal wrote:

Why would you say that if I fly from Bermuda to London it
demonstrates that flights from Bermuda to Algiers and Algiers to
London exist?


Why should I not when I can find interference pattern involving
Algiers and some other city? It is the interference which forces us
to take "the two slit" into account, even with only one photon used
in the process?


It's fine to use some other basis.  We use the "two slit" basis
because that makes the calculations easy.


Yes, but it can be misleading for those who have a naive reading of
the MW. The relevant (for the experience and their relative weigh)
part of the multiverse is base independent (eventually it is even
"theory" independent).





But that's not a reason to say each path is in a different world;
PARTICULARY since they interfere with one another.


That is why I usually avoid the term "world".  "Many-dreams" is less
wrong, and it makes physics looking already closer to the digital
mechanist (non computable) physics.

Bruno






Brent


http://iridia.ulb.ac.be/~marchal/


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Re: A thought on MWI and its alternative(s)

[Pierz]

Bruno, do you believe there is a different world for every possible basis in 
which a spin (or other observable) might be measured? That seems pretty 
strange. 

On Wednesday, June 21, 2017 at 10:27:14 PM UTC+10, Bruno Marchal wrote:
> On 20 Jun 2017, at 19:44, Brent Meeker wrote:
> 
> >
> >
> > On 6/19/2017 11:47 PM, Bruno Marchal wrote:
> >>> Why would you say that if I fly from Bermuda to London it  
> >>> demonstrates that flights from Bermuda to Algiers and Algiers to  
> >>> London exist?
> >>
> >> Why should I not when I can find interference pattern involving  
> >> Algiers and some other city? It is the interference which forces us  
> >> to take "the two slit" into account, even with only one photon used  
> >> in the process?
> >
> > It's fine to use some other basis.  We use the "two slit" basis  
> > because that makes the calculations easy.
> 
> Yes, but it can be misleading for those who have a naive reading of  
> the MW. The relevant (for the experience and their relative weigh)  
> part of the multiverse is base independent (eventually it is even  
> "theory" independent).
> 
> 
> 
> 
> >  But that's not a reason to say each path is in a different world;  
> > PARTICULARY since they interfere with one another.
> 
> That is why I usually avoid the term "world".  "Many-dreams" is less  
> wrong, and it makes physics looking already closer to the digital  
> mechanist (non computable) physics.
> 
> Bruno
> 
> 
> 
> 
> >
> > Brent
> 
> http://iridia.ulb.ac.be/~marchal/

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 20 Jun 2017, at 19:44, Brent Meeker wrote:




On 6/19/2017 11:47 PM, Bruno Marchal wrote:
Why would you say that if I fly from Bermuda to London it  
demonstrates that flights from Bermuda to Algiers and Algiers to  
London exist?


Why should I not when I can find interference pattern involving  
Algiers and some other city? It is the interference which forces us  
to take "the two slit" into account, even with only one photon used  
in the process?


It's fine to use some other basis.  We use the "two slit" basis  
because that makes the calculations easy.


Yes, but it can be misleading for those who have a naive reading of  
the MW. The relevant (for the experience and their relative weigh)  
part of the multiverse is base independent (eventually it is even  
"theory" independent).





 But that's not a reason to say each path is in a different world;  
PARTICULARY since they interfere with one another.


That is why I usually avoid the term "world".  "Many-dreams" is less  
wrong, and it makes physics looking already closer to the digital  
mechanist (non computable) physics.


Bruno






Brent


http://iridia.ulb.ac.be/~marchal/



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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 19 Jun 2017, at 19:08, Brent Meeker wrote:




On 6/19/2017 2:46 AM, Bruno Marchal wrote:

So back to quantum computation: what I think that QC demonstrates
(independently of it being realised by network models or cluster
states) is that the superposition of states really does mean that  
the

various states *exist*.


Superposition of states just means you choose a basis for the  
states that did not have the right eigenstates.  "Being in a  
superpostion" is just a coordinate choice.  It's like saying that  
going from Bermuda to London is a superposition of north-traveling  
and east-traveling.


? That resembles a confusion between pure state and mixed state.


I didn't say anything about mixed states.  I pointed out that any  
pure state can be expressed as a superposition by writing it in  
basis other than its eigenbasis.  This is not unique so which states  
appear in the superposition is matter of choice.  That makes it hard  
to regard them as existing.


I agree it is conceptually hard, but it is logically simple.




I am sure you are aware of the difference so I find this answer  
very weird. It brushes away all the interpretation problem we have  
of the facts (not just the theory). Single photon (or molecule)  
interference would not exist if pure state where not also  
superposition in the rotated base.


Why would you say that if I fly from Bermuda to London it  
demonstrates that flights from Bermuda to Algiers and Algiers to  
London exist?


Why should I not when I can find interference pattern involving  
Algiers and some other city? It is the interference which forces us to  
take "the two slit" into account, even with only one photon used in  
the process?


Bruno





Brent

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Re: A thought on MWI and its alternative(s)

[Pierz]

On Tuesday, June 20, 2017 at 3:08:42 AM UTC+10, Brent wrote:
>
>
>
> On 6/19/2017 2:46 AM, Bruno Marchal wrote:
>
> So back to quantum computation: what I think that QC demonstrates 
> (independently of it being realised by network models or cluster 
> states) is that the superposition of states really does mean that the 
> various states **exist**. 
>
>
> Superposition of states just means you choose a basis for the states that 
> did not have the right eigenstates.  "Being in a superpostion" is just a 
> coordinate choice.  It's like saying that going from Bermuda to London is a 
> superposition of north-traveling and east-traveling. 
>
>
> ? That resembles a confusion between pure state and mixed state. 
>
>
> I didn't say anything about mixed states.  I pointed out that any pure 
> state can be expressed as a superposition by writing it in basis other than 
> its eigenbasis.  This is not unique so which states appear in the 
> superposition is matter of choice.  That makes it hard to regard them as 
> existing.
>
> I am sure you are aware of the difference so I find this answer very 
> weird. It brushes away all the interpretation problem we have of the facts 
> (not just the theory). Single photon (or molecule) interference would not 
> exist if pure state where not also superposition in the rotated base. 
>
>
> Why would you say that if I fly from Bermuda to London it demonstrates 
> that flights from Bermuda to Algiers and Algiers to London exist?  
>

No, but if when nobody is watching you fly, you arrive in London with 
airport souvenirs from Algiers, well...
 

>
> Brent
>

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Re: A thought on MWI and its alternative(s)

[Brent Meeker]

On 6/19/2017 2:46 AM, Bruno Marchal wrote:

So back to quantum computation: what I think that QC demonstrates
(independently of it being realised by network models or cluster
states) is that the superposition of states really does mean that the
various states *exist*.


Superposition of states just means you choose a basis for the states 
that did not have the right eigenstates.  "Being in a superpostion" 
is just a coordinate choice.  It's like saying that going from 
Bermuda to London is a superposition of north-traveling and 
east-traveling.


? That resembles a confusion between pure state and mixed state. 


I didn't say anything about mixed states.  I pointed out that any pure 
state can be expressed as a superposition by writing it in basis other 
than its eigenbasis.  This is not unique so which states appear in the 
superposition is matter of choice.  That makes it hard to regard them as 
existing.


I am sure you are aware of the difference so I find this answer very 
weird. It brushes away all the interpretation problem we have of the 
facts (not just the theory). Single photon (or molecule) interference 
would not exist if pure state where not also superposition in the 
rotated base. 


Why would you say that if I fly from Bermuda to London it demonstrates 
that flights from Bermuda to Algiers and Algiers to London exist?


Brent

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 18 Jun 2017, at 21:17, Brent Meeker wrote:




On 6/18/2017 3:43 AM, Telmo Menezes wrote:

No, but it does mean that a quantum computer can have the
computational power of a lot of Turing machines acting in parallel,
and it is normal to ask "why?", and be unsatisfied with a theory  
that

does not answer this question.


I have come across an interesting paper that discusses these  
questions, and
comes to the conclusion that it is problematic to see quantum  
computing as

accessing the computing power of other worlds.

Michael Cuffaro, http://arxiv.org/abs/1110.2514v2
Thanks for the paper, I finally had some time to read it. I also  
write

in reply to Brent, I think we are all talking about the same thing.

First of all: I was too quick in accepting your definition of  
world. I

think this is where our disagreement starts. You define a world
bottom-up, by saying that if two thing can interact, then they belong
to the same world. I would say that this is a good definition for
classical worlds, but it becomes useless when it is not longer clear
what "things" are these that can interact.

I prefer this definition: a world is the set of things that can be
observed. My definition forces one to invite theories of mind into  
the

discussion. This is another thing I was too quick to accept: to talk
about "just physics". When we are discussing interpretations of QM,
it's no longer "just physics". Such a requirement makes the  
discussion

non-sensical.

To be clear, let us consider the double-slit experiment.
Simplistically, under my definition there are three possible worlds:
the two ones where you know which sensor was activated and there is  
no

interference, and the one where you do not know and there is
interference. The knowing/now knowing distinction is key here. The
world-as-what-can-be-observed can supervene on different subsets of
the totality, depending on which degrees of freedom are conserved. If
I can know which sensor was activated, then the world where I'm in is
not compatible with a superposition of states on the electron, and no
interference is observable. This is the fundamental breakdown of
"thingness" that QM brings to the table.

So back to quantum computation: what I think that QC demonstrates
(independently of it being realised by network models or cluster
states) is that the superposition of states really does mean that the
various states *exist*.


Superposition of states just means you choose a basis for the states  
that did not have the right eigenstates.  "Being in a superpostion"  
is just a coordinate choice.  It's like saying that going from  
Bermuda to London is a superposition of north-traveling and east- 
traveling.


? That resembles a confusion between pure state and mixed state. I am  
sure you are aware of the difference so I find this answer very weird.  
It brushes away all the interpretation problem we have of the facts  
(not just the theory). Single photon (or molecule) interference would  
not exist if pure state where not also superposition in the rotated  
base.


Bruno








They are necessarily things, because they
provide a subtract for computation that does not exist otherwise. If
you wanted to deny this, you would have to be able to show me that
your interpretation of QC can be used to implement an equally  
powerful

algorithm in a classical computer. But you cannot do that, cluster
state or not. This is what makes purely probabilistic interpretations
awkward, and I think this is the meat of Deutsch's intuition.

I think that the preferred basis problem operates at a lower level
than what I think is a useful definition of world. It's just a matter
of frame of reference. It's like refuting the idea that the Earth
follows and approximately elliptical orbit around the Sun by placing
the frame of reference in Venus. Both descriptions are valid, but the
first makes it easier to apprehend the actual underlying phenomenon.
An Ptolemy would have said it's a superposition of epicycles. That's  
no reason to reify epicycles.


For me, the underlying phenomenon here is about what mind can
supervene on. Refusing to do this exercise seems absurd, because the
very point of interpreting quantum mechanics is to figure out what is
the reality that the equations describe, taking into account the
reality that we can observe. If we remove the problem of mind from  
the

effort, there is no ground to stand on.
But if you take mind to supervene on the physics then observation  
is just another physical interaction. What about it makes it  
"underlying" or a something to define reality?  As you know, I  
resist the temptation to designate something as "fundamental".   
I'd like to have an explanation of physics in terms of mind or  
computation and vice versa.
But if you take mind to supervene on the physics then observation is  
just another physical interaction. What about it makes it  
"underlying" or a something to define reality?  As you know, I  
resist the temptat

Re: A thought on MWI and its alternative(s)

[Brent Meeker]

On 6/18/2017 3:43 AM, Telmo Menezes wrote:

No, but it does mean that a quantum computer can have the
computational power of a lot of Turing machines acting in parallel,
and it is normal to ask "why?", and be unsatisfied with a theory that
does not answer this question.


I have come across an interesting paper that discusses these questions, and
comes to the conclusion that it is problematic to see quantum computing as
accessing the computing power of other worlds.

Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Thanks for the paper, I finally had some time to read it. I also write
in reply to Brent, I think we are all talking about the same thing.

First of all: I was too quick in accepting your definition of world. I
think this is where our disagreement starts. You define a world
bottom-up, by saying that if two thing can interact, then they belong
to the same world. I would say that this is a good definition for
classical worlds, but it becomes useless when it is not longer clear
what "things" are these that can interact.

I prefer this definition: a world is the set of things that can be
observed. My definition forces one to invite theories of mind into the
discussion. This is another thing I was too quick to accept: to talk
about "just physics". When we are discussing interpretations of QM,
it's no longer "just physics". Such a requirement makes the discussion
non-sensical.

To be clear, let us consider the double-slit experiment.
Simplistically, under my definition there are three possible worlds:
the two ones where you know which sensor was activated and there is no
interference, and the one where you do not know and there is
interference. The knowing/now knowing distinction is key here. The
world-as-what-can-be-observed can supervene on different subsets of
the totality, depending on which degrees of freedom are conserved. If
I can know which sensor was activated, then the world where I'm in is
not compatible with a superposition of states on the electron, and no
interference is observable. This is the fundamental breakdown of
"thingness" that QM brings to the table.

So back to quantum computation: what I think that QC demonstrates
(independently of it being realised by network models or cluster
states) is that the superposition of states really does mean that the
various states *exist*.


Superposition of states just means you choose a basis for the states 
that did not have the right eigenstates.  "Being in a superpostion" is 
just a coordinate choice.  It's like saying that going from Bermuda to 
London is a superposition of north-traveling and east-traveling.



They are necessarily things, because they
provide a subtract for computation that does not exist otherwise. If
you wanted to deny this, you would have to be able to show me that
your interpretation of QC can be used to implement an equally powerful
algorithm in a classical computer. But you cannot do that, cluster
state or not. This is what makes purely probabilistic interpretations
awkward, and I think this is the meat of Deutsch's intuition.

I think that the preferred basis problem operates at a lower level
than what I think is a useful definition of world. It's just a matter
of frame of reference. It's like refuting the idea that the Earth
follows and approximately elliptical orbit around the Sun by placing
the frame of reference in Venus. Both descriptions are valid, but the
first makes it easier to apprehend the actual underlying phenomenon.
An Ptolemy would have said it's a superposition of epicycles. That's no 
reason to reify epicycles.


For me, the underlying phenomenon here is about what mind can
supervene on. Refusing to do this exercise seems absurd, because the
very point of interpreting quantum mechanics is to figure out what is
the reality that the equations describe, taking into account the
reality that we can observe. If we remove the problem of mind from the
effort, there is no ground to stand on.
But if you take mind to supervene on the physics then observation is 
just another physical interaction. What about it makes it 
"underlying" or a something to define reality?  As you know, I resist 
the temptation to designate something as "fundamental".  I'd like to 
have an explanation of physics in terms of mind or computation and 
vice versa.
But if you take mind to supervene on the physics then observation is 
just another physical interaction. What about it makes it "underlying" 
or a something to define reality?  As you know, I resist the temptation 
to designate something as "fundamental".  I'd like to have an 
explanation of physics in terms of mind and vice versa.


If you want to take mind as basic then it seems that QBism is the proper 
interpretation of QM.  Most physicist dislike it because it is personal 
- each person has their own idea of the wave function - but that strikes 
me as a necessary aspect of a mind-based interpretation.



  It's just a popularity contest
between equally unfalsifiable 

Re: A thought on MWI and its alternative(s)

[spudboy100 via Everything List]

The Michael Cuffaro associated paper is a thesis of David Deutsch at Oxford 
from 20 years ago (and more). Deutsch also holds that we cannot in principle 
contact our own past, but an exact, parallel Earth is doable (in theory), so 
you can assassinate your clone's grandfather. For me, my imaginary fun time, 
side thinks, trade and adventure between earths. In the same spirit as trade 
and adventure crossing the galaxy. The Deutsch thing on alternate cosmos 
computing power sounds phenomenal too, but that is too real world for me.  



-Original Message-
From: Telmo Menezes 
To: everything-list 
Sent: Sun, Jun 18, 2017 6:43 am
Subject: Re: A thought on MWI and its alternative(s)

> No, but it does mean that a quantum computer can have the
> computational power of a lot of Turing machines acting in parallel,
> and it is normal to ask "why?", and be unsatisfied with a theory that
> does not answer this question.
>
>
> I have come across an interesting paper that discusses these questions, and
> comes to the conclusion that it is problematic to see quantum computing as
> accessing the computing power of other worlds.
>
> Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Thanks for the paper, I finally had some time to read it. I also write
in reply to Brent, I think we are all talking about the same thing.

First of all: I was too quick in accepting your definition of world. I
think this is where our disagreement starts. You define a world
bottom-up, by saying that if two thing can interact, then they belong
to the same world. I would say that this is a good definition for
classical worlds, but it becomes useless when it is not longer clear
what "things" are these that can interact.

I prefer this definition: a world is the set of things that can be
observed. My definition forces one to invite theories of mind into the
discussion. This is another thing I was too quick to accept: to talk
about "just physics". When we are discussing interpretations of QM,
it's no longer "just physics". Such a requirement makes the discussion
non-sensical.

To be clear, let us consider the double-slit experiment.
Simplistically, under my definition there are three possible worlds:
the two ones where you know which sensor was activated and there is no
interference, and the one where you do not know and there is
interference. The knowing/now knowing distinction is key here. The
world-as-what-can-be-observed can supervene on different subsets of
the totality, depending on which degrees of freedom are conserved. If
I can know which sensor was activated, then the world where I'm in is
not compatible with a superposition of states on the electron, and no
interference is observable. This is the fundamental breakdown of
"thingness" that QM brings to the table.

So back to quantum computation: what I think that QC demonstrates
(independently of it being realised by network models or cluster
states) is that the superposition of states really does mean that the
various states *exist*. They are necessarily things, because they
provide a subtract for computation that does not exist otherwise. If
you wanted to deny this, you would have to be able to show me that
your interpretation of QC can be used to implement an equally powerful
algorithm in a classical computer. But you cannot do that, cluster
state or not. This is what makes purely probabilistic interpretations
awkward, and I think this is the meat of Deutsch's intuition.

I think that the preferred basis problem operates at a lower level
than what I think is a useful definition of world. It's just a matter
of frame of reference. It's like refuting the idea that the Earth
follows and approximately elliptical orbit around the Sun by placing
the frame of reference in Venus. Both descriptions are valid, but the
first makes it easier to apprehend the actual underlying phenomenon.

For me, the underlying phenomenon here is about what mind can
supervene on. Refusing to do this exercise seems absurd, because the
very point of interpreting quantum mechanics is to figure out what is
the reality that the equations describe, taking into account the
reality that we can observe. If we remove the problem of mind from the
effort, there is no ground to stand on. It's just a popularity contest
between equally unfalsifiable hypothesis.

> The explanation for exponential speedup is:
> "On this view, quantum computers are faster than classical computers because
> they perform fewer, not more, computations.

This is just circular reasoning, taking advantage of ambiguity on how
to count computations -- and begging the question when deciding how to
count them. Otherwise, give me the algorithm so that I can test it
here, on my laptop.

Telmo.

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Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

> No, but it does mean that a quantum computer can have the
> computational power of a lot of Turing machines acting in parallel,
> and it is normal to ask "why?", and be unsatisfied with a theory that
> does not answer this question.
>
>
> I have come across an interesting paper that discusses these questions, and
> comes to the conclusion that it is problematic to see quantum computing as
> accessing the computing power of other worlds.
>
> Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Thanks for the paper, I finally had some time to read it. I also write
in reply to Brent, I think we are all talking about the same thing.

First of all: I was too quick in accepting your definition of world. I
think this is where our disagreement starts. You define a world
bottom-up, by saying that if two thing can interact, then they belong
to the same world. I would say that this is a good definition for
classical worlds, but it becomes useless when it is not longer clear
what "things" are these that can interact.

I prefer this definition: a world is the set of things that can be
observed. My definition forces one to invite theories of mind into the
discussion. This is another thing I was too quick to accept: to talk
about "just physics". When we are discussing interpretations of QM,
it's no longer "just physics". Such a requirement makes the discussion
non-sensical.

To be clear, let us consider the double-slit experiment.
Simplistically, under my definition there are three possible worlds:
the two ones where you know which sensor was activated and there is no
interference, and the one where you do not know and there is
interference. The knowing/now knowing distinction is key here. The
world-as-what-can-be-observed can supervene on different subsets of
the totality, depending on which degrees of freedom are conserved. If
I can know which sensor was activated, then the world where I'm in is
not compatible with a superposition of states on the electron, and no
interference is observable. This is the fundamental breakdown of
"thingness" that QM brings to the table.

So back to quantum computation: what I think that QC demonstrates
(independently of it being realised by network models or cluster
states) is that the superposition of states really does mean that the
various states *exist*. They are necessarily things, because they
provide a subtract for computation that does not exist otherwise. If
you wanted to deny this, you would have to be able to show me that
your interpretation of QC can be used to implement an equally powerful
algorithm in a classical computer. But you cannot do that, cluster
state or not. This is what makes purely probabilistic interpretations
awkward, and I think this is the meat of Deutsch's intuition.

I think that the preferred basis problem operates at a lower level
than what I think is a useful definition of world. It's just a matter
of frame of reference. It's like refuting the idea that the Earth
follows and approximately elliptical orbit around the Sun by placing
the frame of reference in Venus. Both descriptions are valid, but the
first makes it easier to apprehend the actual underlying phenomenon.

For me, the underlying phenomenon here is about what mind can
supervene on. Refusing to do this exercise seems absurd, because the
very point of interpreting quantum mechanics is to figure out what is
the reality that the equations describe, taking into account the
reality that we can observe. If we remove the problem of mind from the
effort, there is no ground to stand on. It's just a popularity contest
between equally unfalsifiable hypothesis.

> The explanation for exponential speedup is:
> "On this view, quantum computers are faster than classical computers because
> they perform fewer, not more, computations.

This is just circular reasoning, taking advantage of ambiguity on how
to count computations -- and begging the question when deciding how to
count them. Otherwise, give me the algorithm so that I can test it
here, on my laptop.

Telmo.

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 16 Jun 2017, at 04:21, Bruce Kellett wrote:


On 15/06/2017 6:01 pm, Bruno Marchal wrote:

On 14 Jun 2017, at 01:06, Bruce Kellett wrote:

You seem to be taking the older view of many worlds that is  
favoured by David Deutsch. This approach has serious problems with  
the notorious basis problem, and there does not seem to be any  
principled way from within the theory to select unambiguosly the  
basis in which all of these worlds form. More recent  
understandings of MWI take decoherence into account. Decoherence  
provides a principled dynamical way to solve the basis problem,  
but it means the worlds do not actually form until there is  
decoherence -- worlds cannot form until they know what basis is  
relevant!


I recommend the paper I suggested to Telmo:

Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Cuffaro discusses the problems with the older form of MWI and  
suggests that although many worlds might be a useful heuristic in  
quantum computing, decoherence is required before worlds could be  
considered to have any ontological basis. The exponential speedup  
with a quantum computer is then seen in the fact that the QC  
manipulates the phases inherent in the entanglement of qbits, and  
doesn't have to actually calculate the function in question for  
all possible inputs, as the older many worlds view requires.




Oh! I see that my explanation that the MW prevents the need of  
action at a distance was neo-everettian!


Well, no! Your explanation was not anything at all because you have  
not given an explanation, despite my asking many times. The best you  
have managed is some general comments and a lot of hand-waving.


Rhetorical trick. The linearity of evolution, and tensor product, and  
interaction makes just impossible any action action at a distance. I  
might say that you are the one imposing some unclear interpretation of  
"world" so that you can extract from the bell's violation some spoky  
action at a distance. That does not make sense in special relativity.






I am not sure I understand the paper by Currafo, as I have no  
single-world interpretation of entanglement and/or quantum phase.


That must be a considerable disadvantage for you! Entanglement is  
universal in quantum mechanics: every time objects interact they  
become entangled.


Yes, that is why I consider the Aspect experience as an evidence for  
the MW. I agree that Bells violation in one world entails action at a  
distance.






Entanglement is at the basis of the emergence of a classical world,  
and since we only ever experience just one world, we must have a  
single-world understanding of entanglement.


We need only a theory of mind, and Everett use mechanism. Only  
problem: with mechanism we have to derive the physics as a first  
plural self-referential reality. But it works already rather well at  
the propositional level.




I don't know what you mean by no single-world interpretation of a  
quantum phase. A quantum phase is just an angle like any other.


But "quantum" is the subject on which we search an interpretation for.

To me, MW is the same as QM-without collapse axioms. I use it  
informally and formally to compare with the internal many dreams  
interpretation of arithmetic, that the numbers can discuss in  
arithmetical forum.







I think the problem you face is always going to be that of finding a  
basis that is not ad hoc.



The basis, like the histories in arithmetic, are chosen from inside,  
indexically. Consciousness can only differentiate on distinguishable  
realities, choosing the bases is a bit like choosing your parents.






If you see every superposition as a matter of multiple worlds, then  
you have no interpretation of a pure quantum state. As Brent (and  
everyone else) points out, a pure state is not a superposition in  
the basis in which that state is one of the basis vectors, and there  
are an infinite number of other bases in which it is a  
superposition. So what are you going to choose? One world or an  
infinity of different incompatible worlds?


Define world.

I assume only 0, s, + x usual sense.

And I agree it is weird. A particle with a precise position is a  
particle with an imprecise impulsion, so you have the choice to  
partitioned the mutltiverse in different relative way. If you see that  
this is an argument against the notion of worlds, OK, it might be a  
good new for the mechanist, because we do have a serious measure  
problem, and we still not have the "Gleason theorem", but we do have  
three quantum logics, so let us see.


I do not defend any theory. I am a logician. I just show that If we  
survive a digital brain transplant, then physics has to be retrieved  
from the logic of self-reference on the sigma sentence. That works.










At best, it would be a critics of the notion of world (be it single  
or not), and this would made QM even closer to the physics  
extracted from computationalism, where there is no worl

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 15/06/2017 6:01 pm, Bruno Marchal wrote:

On 14 Jun 2017, at 01:06, Bruce Kellett wrote:

You seem to be taking the older view of many worlds that is favoured 
by David Deutsch. This approach has serious problems with the 
notorious basis problem, and there does not seem to be any principled 
way from within the theory to select unambiguosly the basis in which 
all of these worlds form. More recent understandings of MWI take 
decoherence into account. Decoherence provides a principled dynamical 
way to solve the basis problem, but it means the worlds do not 
actually form until there is decoherence -- worlds cannot form until 
they know what basis is relevant!


I recommend the paper I suggested to Telmo:

Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Cuffaro discusses the problems with the older form of MWI and 
suggests that although many worlds might be a useful heuristic in 
quantum computing, decoherence is required before worlds could be 
considered to have any ontological basis. The exponential speedup 
with a quantum computer is then seen in the fact that the QC 
manipulates the phases inherent in the entanglement of qbits, and 
doesn't have to actually calculate the function in question for all 
possible inputs, as the older many worlds view requires.




Oh! I see that my explanation that the MW prevents the need of action 
at a distance was neo-everettian!


Well, no! Your explanation was not anything at all because you have not 
given an explanation, despite my asking many times. The best you have 
managed is some general comments and a lot of hand-waving.


I am not sure I understand the paper by Currafo, as I have no 
single-world interpretation of entanglement and/or quantum phase.


That must be a considerable disadvantage for you! Entanglement is 
universal in quantum mechanics: every time objects interact they become 
entangled. Entanglement is at the basis of the emergence of a classical 
world, and since we only ever experience just one world, we must have a 
single-world understanding of entanglement. I don't know what you mean 
by no single-world interpretation of a quantum phase. A quantum phase is 
just an angle like any other.


I think the problem you face is always going to be that of finding a 
basis that is not ad hoc. If you see every superposition as a matter of 
multiple worlds, then you have no interpretation of a pure quantum 
state. As Brent (and everyone else) points out, a pure state is not a 
superposition in the basis in which that state is one of the basis 
vectors, and there are an infinite number of other bases in which it is 
a superposition. So what are you going to choose? One world or an 
infinity of different incompatible worlds?


At best, it would be a critics of the notion of world (be it single or 
not), and this would made QM even closer to the physics extracted from 
computationalism, where there is no world at all, and the 
differentiation is only a relative differentiation of the 
consciousness of a person. I guess mechanism is probably 
neo-neo-everettian, if not neo-neo-neo-Everettian. As I said once, 
despite Everett seems to disagree, it is better to talk in term of 
relative state, or relative dreams, instead of world. The worlds, with 
mechanism, are maximal consistent extensions, and exists only in the 
mind of the numbers. The FPI are not on the worlds, but on the first 
person (hopefully plural, as it seems) experience.


Probably more on this later, I have still a lot of work to do. 
Meanwhile, Bruce, or anyone, you might try to explain his cluster 
quantum computing in a single world, or with collapse. Cuffaro does 
not provide any explanation of this, and when taken literally, his 
multi-qubit entanglement requires "MW" (or many minds, many dreams, 
many numbers, etc.).


I am not an expert in quantum computing, but I though Cuffaro's paper 
was relatively self-explanatory. The basis problem effectively sinks the 
many-worlds interpretation of quantum computing. Of course, if you have 
difficulty in understanding entanglement in one world, then you might 
have trouble with the multiple entangled qbits involved in cluster QC. 
But the fact that there is no single basis in which this entangled 
cluster can be interpreted -- the measurement bases are adaptive from 
one qbit to the next -- makes any many-worlds interpretation extremely 
cumbersome and artificial.


The bottom line in all of this is the need to have a definite basis in 
which one's many-worlds are to be defined. QC does not appear to have 
any principled way to define such a basis, whereas what Cuffaro calls 
neo-Everettian approaches do -- one simply uses the basic dynamics to 
define a basis that is stable against environmental decoherence. That 
give a suitable basis in a way that is not ad hoc or circular.


Bruce

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Re: A thought on MWI and its alternative(s)

[John Clark]

On Tue, Jun 13, 2017 at 7:11 AM, Telmo Menezes 
wrote:

​> ​
>  If you take the wave function seriously, then you take
> ​ ​
> seriously that qubits really do exist in a superposition of states,
> ​ ​
> and this explains the exponential increase in computational power as
> ​ ​
> you add qubits to the systems in certain configurations. I guess you
> ​ ​
> can accept superposition and deny many worlds, but I would say that it
> ​ ​
> is quite an awkward move.


Actually you can do Quantum Mechanics without making use of the wave
equation,
​ ​
Heisenberg
​ ​
found a way of doing it about 6 months before Schrodinger discovered his
equation. Both methods produced the same answer but Heisenberg's way was
more abstract and for most (but not all) problems the calculations were
more complex. Most physicists decided Quantum Mechanics was abstract and
complex enough as it is so Schrodinger's Wave Equation is usually their
first choice.  In the same way if you were a working stiff who made his
living writing quantum programs I suppose you could try to find the bug in
your incomplete program
​ ​
by
​ ​
visualizing
​ ​
Copenhagen, but I think you'd get
​a ​
better
​understanding of how your program works and the errors in it by​
 visualizing Many Worlds.

  ​John K Clark​

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 15 Jun 2017, at 06:59, Bruce Kellett wrote:



On Wednesday, June 14, 2017 at 10:19:56 AM UTC+10, Brent wrote
6/13/2017 4:11 AM, Telmo Menezes wrote:

> The reason why it would follow is precisely the point of my  
rhetorical
> question above. If you take the wave function seriously, then you  
take

> seriously that qubits really do exist in a superposition of states,
> and this explains the exponential increase in computational power as
> you add qubits to the systems in certain configurations. I guess you
> can accept superposition and deny many worlds, but I would say  
that it

> is quite an awkward move.

Being in a superposition is just a matter choosing the basis.  If  
it's a

pure state then there's some basis in which it is not a superposition.
And if it's not in a superposition, then you can choose another  
basis in

which it is.

The basis problem is always going to defeat naive accounts of many  
worlds.


OK.



That is why most people now see decoherence as central, since that  
can give a principle reason for basis selection: the preferred basis  
is that which is stable against environmental decoherence.


That was already well explained in Everett's long text. But the  
preferred basis is only preferred relatively to a entity/machine. The  
big picture does not need to choose a special base. That is proven in  
Everett. He insisted that this makes the notion of subsystem into a  
relative notion.





Separate worlds can only form after irreversible decoherence.



The decoherence itself is reversible in QM-without collapse, and it  
can even been done, theoretically, by memory erasing/discarding. Of  
course, to have a decent subjective life for some period, it is better  
(FAPP) to consider the decoherence irreversible. Yet, to avoid  
conceptual paradoxes, we need to realize that, without collapse, the  
decoherence is always a local happening and is *in principle  
reversible* in the big picture. The entire universe (assuming this  
makes some sense) cannot be subjected to decoherence, as you cannot  
leak outside the universe, by definition of "universe".


Bruno





Bruce

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 14 Jun 2017, at 19:11, John Clark wrote:

On Wed, Jun 14, 2017 at 5:01 AM, Bruno Marchal   
wrote:


​>> ​Even the 2-slit experiment will not produce interference if  
you remove the photographic plate and just allow the photons to  
continue into infinite space after they pass the slits because then  
the world splits but the two never recombine again so no interference.


​> ​This is a bit weird. I would say that the interference are  
still there, but that we can't see them.


I don't see why you would say that. We know for a fact from  
experiment that you CAN place a detector next to one slit so you CAN  
know which slit the photon went through, but if you do that then the  
interference pattern disappears. How does the MWI explain that?  It  
says that when the photon approaches the 2 slits the universe  
splits, but in one universe a record is made (in a computer or a  
paper notebook or a human memory) that the photon went through the  
left slot and in the other a record is made that the photon went  
through the right slot. When the photon hits the photographic plate  
it's destroyed but the 2 universes are still NOT identical because  
they have different records, so they never merge back together,   
there is nothing to interfere with, so nobody in either universe  
sees a interference pattern.


It would work the same way if no record of which slots the photon  
went through was made but you removed the photographic plate (or  
brick wall) and so didn't destroy it and allowed the photon to  
continue on for eternity after they pass the slits. The photons will  
be on slightly different tracks for infinity and so the two  
universes will never merge together into one and so there is no  
interference between the two.


​> ​Without the photographic plate, we can still introduce a  
needle at a position where no photon will ever go,


​Not after the photon passes the slits you can't, you could never  
move ​your needle fast enough to get in front of it. And according  
to Quantum Mechanics there is no place you can say with certainty  
the photon will never go, but it can tell you that it is more likely  
to go some places than others. You could make a calculation  
beforehand and find a good point to place the needle and bet the  
photon will not hit it, in most universes you will win your bet but   
in some you will not. And one needle is not enough, to prove if  
interference did or did not occur, you'd need lots of photons and  
lots of needles, although a photographic plate would be much easier  
to use.


OK. But so we agree.




​> ​Interferences occur independently of our decision to observe  
them.


​Yes, observation has nothing to do ​with it if the MWI is  
correct, however interference requires at least 2 things, and if  
nothing interferes with the universe no interference pattern will be  
produced; the 2 universes need to merge back together but that will  
never happen if they remain different (because a record of which  
slot the photon went through is different or because the path the  
photon is taking on its infinite voyage is different).


OK.

Bruno





 John K Clark




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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 14 Jun 2017, at 01:06, Bruce Kellett wrote:

You seem to be taking the older view of many worlds that is favoured  
by David Deutsch. This approach has serious problems with the  
notorious basis problem, and there does not seem to be any  
principled way from within the theory to select unambiguosly the  
basis in which all of these worlds form. More recent understandings  
of MWI take decoherence into account. Decoherence provides a  
principled dynamical way to solve the basis problem, but it means  
the worlds do not actually form until there is decoherence -- worlds  
cannot form until they know what basis is relevant!


I recommend the paper I suggested to Telmo:

Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Cuffaro discusses the problems with the older form of MWI and  
suggests that although many worlds might be a useful heuristic in  
quantum computing, decoherence is required before worlds could be  
considered to have any ontological basis. The exponential speedup  
with a quantum computer is then seen in the fact that the QC  
manipulates the phases inherent in the entanglement of qbits, and  
doesn't have to actually calculate the function in question for all  
possible inputs, as the older many worlds view requires.




Oh! I see that my explanation that the MW prevents the need of action  
at a distance was neo-everettian!


I am not sure I understand the paper by Currafo, as I have no single- 
world interpretation of entanglement and/or quantum phase. At best, it  
would be a critics of the notion of world (be it single or not), and  
this would made QM even closer to the physics extracted from  
computationalism, where there is no world at all, and the  
differentiation is only a relative differentiation of the  
consciousness of a person. I guess mechanism is probably neo-neo- 
everettian, if not neo-neo-neo-Everettian. As I said once, despite  
Everett seems to disagree, it is better to talk in term of relative  
state, or relative dreams, instead of world. The worlds, with  
mechanism, are maximal consistent extensions, and exists only in the  
mind of the numbers. The FPI are not on the worlds, but on the first  
person (hopefully plural, as it seems) experience.


Probably more on this later, I have still a lot of work to do.  
Meanwhile, Bruce, or anyone, you might try to explain his cluster  
quantum computing in a single world, or with collapse. Cuffaro does  
not provide any explanation of this, and when taken literally, his  
multi-qubit entanglement requires "MW" (or many minds, many dreams,  
many numbers, etc.).


Bruno






Bruce



On 14/06/2017 4:09 am, John Clark wrote:
On Mon, Jun 12, 2017 at 8:32 PM, Bruce Kellett > wrote:


​ >> ​ ​I agree Interference must take place in a single  
world, but where did all the information that produced the  
interference come from, where did the computations that produced  
all those wrong answers (and a few correct ones) come from?


​ > ​ What calculations are performed in these parallel worlds?

​Whatever algorithm you and your ​doppelgangers decided to run  
on their quantum computer.


​ > ​ And what performs those calculations?

​Computers made of matter that obey the laws of physics.

​ > ​ You are the one who insists that calculation is possible  
only on a physical computer.


​Yes, but you almost make that sound as if it were a contradiction  
of some sort.


​ > ​ Who constructed all these physical computers in the  
parallel worlds?


​If the MWI is correct and if you're a computer engineer then ​  
you and your ​doppelganger ​ s​   ​ made the quantum  
computer, made lots and lots of them actually.


​ >> ​ Even the 2-slit experiment will not produce interference  
if you remove the photographic plate and just allow the photons to  
continue into infinite space after they pass the slits because then  
the world splits but the two never recombine again so no  
interference.


​ > ​ Of course the interference continues -- for ever if  
necessary. The screen or photographic plate is only there to enable  
you to see it.


​No, in the ​Many World's theory it doesn't matter if anybody  
sees the results, in fact a brick wall would work just as well as a  
screen or a photographic plate, the only thing the MWI is  
interested in is that all of those things destroy the photon.


After the photon passed the slits that photon was the only  
difference between those 2 universes, when it is destroyed in both  
universes by a screen or photographic plate or brick wall there is  
no longer a difference between universes so they merge back  
together, but indications it went through slot A and indications it  
went through slot B remain. And that produces the interference  
pattern. We don't usually see this weird quantum effect in our  
everyday macro-world because when a large change is made between  
universes it's hard to arrange things so they evolve together  
toward the same point, become the identical again, and thus 

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On Wednesday, June 14, 2017 at 10:19:56 AM UTC+10, Brent wrote

   6/13/2017 4:11 AM, Telmo Menezes wrote:

> The reason why it would follow is precisely the point of my
   rhetorical
> question above. If you take the wave function seriously, then you
   take
> seriously that qubits really do exist in a superposition of states,
> and this explains the exponential increase in computational power as
> you add qubits to the systems in certain configurations. I guess you
> can accept superposition and deny many worlds, but I would say
   that it
> is quite an awkward move.

   Being in a superposition is just a matter choosing the basis.  If
   it's a
   pure state then there's some basis in which it is not a superposition.
   And if it's not in a superposition, then you can choose another
   basis in
   which it is.


The basis problem is always going to defeat naive accounts of many 
worlds. That is why most people now see decoherence as central, since 
that can give a principle reason for basis selection: the preferred 
basis is that which is stable against environmental decoherence. 
Separate worlds can only form after irreversible decoherence.


Bruce

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Re: A thought on MWI and its alternative(s)

[John Clark]

On Wed, Jun 14, 2017 at 5:01 AM, Bruno Marchal  wrote:


> ​>> ​
>> Even the 2-slit experiment will not produce interference if you remove
>> the photographic plate and just allow the photons to continue into infinite
>> space after they pass the slits because then the world splits but the two
>> never recombine again so no interference.
>
>
> ​> ​
> This is a bit weird. I would say that the interference are still there,
> but that we can't see them.
>

I don't see why you would say that. We know for a fact from experiment that
you CAN place a detector next to one slit so you CAN know which slit the
photon went through, but if you do that then the interference pattern
disappears. How does the MWI explain that?  It says that when the photon
approaches the 2 slits the universe splits, but in one universe a record is
made (in a computer or a paper notebook or a human memory) that the photon
went through the left slot and in the other a record is made that the
photon went through the right slot. When the photon hits the photographic
plate it's destroyed but the 2 universes are still NOT identical because
they have different records, so they never merge back together,  there is
nothing to interfere with, so nobody in either universe sees a interference
pattern.

It would work the same way if no record of which slots the photon went
through was made but you removed the photographic plate (or brick wall) and
so didn't destroy it and allowed the photon to continue on for eternity
after they pass the slits. The photons will be on slightly different tracks
for infinity and so the two universes will never merge together into one
and so there is no interference between the two.


> ​> ​
> Without the photographic plate, we can still introduce a needle at a
> position where no photon will ever go,
>

​Not after the photon passes the slits you can't, you could never move
​your needle fast enough to get in front of it. And according to Quantum
Mechanics there is no place you can say with certainty the photon will
never go, but it can tell you that it is more likely to go some places than
others. You could make a calculation beforehand and find a good point to
place the needle and bet the photon will not hit it, in most universes you
will win your bet but  in some you will not. And one needle is not enough,
to prove if interference did or did not occur, you'd need lots of photons
and lots of needles, although a photographic plate would be much easier to
use.


> ​> ​
> Interferences occur independently of our decision to observe them.
>

​Yes, observation has nothing to do ​with it if the MWI is correct, however
interference requires at least 2 things, and if nothing interferes with the
universe no interference pattern will be produced; the 2 universes need to
merge back together but that will never happen if they remain different
(because a record of which slot the photon went through is different or
because the path the photon is taking on its infinite voyage is different).

 John K Clark

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 12 Jun 2017, at 17:09, John Clark wrote:

On Fri, Jun 9, 2017 at 7:11 PM, Bruce Kellett > wrote:


​> ​Deutsch is out to lunch on this. He appears to assume that a  
quantum computer is just using the same algorithms that a classical  
computer would use, only executing them in a massively parallel  
manner.


​As Deutsch is ​probably only the second person (after Richard  
Feynman) to think long and hard about quantum computers I'm pretty  
sure he doesn't believe that just any old algorithm will do, and I'm  
even more sure he doesn't believe the classical hardware we use in  
our computers today can take advantage of a quantum speedup.


The miniaturisation of the concrete cassical computers of today has  
been made possible thanks to quantum mechanics. In fact, the discovery  
of the transistor has been made through the solving of Schrodinger  
equation. But classical computer, which are quantum object like any  
piece of matter, does not exploit the quantum in his way of computing.  
We could in principle do that, if we were able to isolated them enough  
from their environment, but this is quasi impossible today.







 ​>Scott Aaronson points out:
"The way a quantum algorithms work is that they arrange for wrong  
answers to destructively interfere while the desired answer  
interferes constructively. Interference requires that they take  
place in the same world."


​I agree Interference must take place in a single world,


I would say: in a single multiverse. "World" is ambiguous, because in  
some context it denote a branch of the universal wave, and sometimes  
the universal wave itself.





but where did all the information that produced the interference  
come from, where did the computations that produced all those wrong  
answers (and a few correct ones) come from? Even the 2-slit  
experiment will not produce interference if you remove the  
photographic plate and just allow the photons to continue into  
infinite space after they pass the slits because then the world  
splits but the two never recombine again so no interference.


This is a bit weird. I would say that the interference are still  
there, but that we can't see them. Without the photographic plate, we  
can still introduce a needle at a position where no photon will ever  
go, because of the destructive interference due to the two slits open.  
If we accept Einstein reality principle, we know that even without  
that needle, no photon can ever appears at such a position.  
Interferences occur independently of our decision to observe them.





You need places for things to become different and also a place for  
things to come together again for interference to occur.


​>Quantum computing does not prove the existence of parallel worlds  
-- there is no need for other worlds in which to find the  
computational power,


​A large Quantum Computer wouldn't prove beyond any logical doubt  
that other world's must exist, but then you don't exactly "need"  
a​ ​heliocentric​ ​solar system theory to explain the  
movements of the planets either;​ ​you could stick with the Earth  
centered model if you added enough epicycles of the type used by  
Ptolemy 2000 years ago​.​ ​T​hen the way the planets moved in  
relation to the crystalline celestial sphere​,​​ ​the one  
that ​has ​the stars painted on​ it, ​could be​ ​ 
predicted​ ​to the limits​ ​of observational accuracy. But  
you'd need a awful lot of​ ​epicycles and calculations would  
literally ​be ​astronomically more complex than with the​ ​ 
far simpler​ ​heliocentric​ ​model.


OK.





In the same way I think when quantum computers become commonplace  
programers will ​take ​Many Worlds as a given even if they ​ 
can't​ formally prove they exist because it's just easier to  
visualize how they work that way, just as it's easier to visualize a  
few elliptical orbit​s​ around the sun than​ ​visualize a  
gazilian​ ​circles around circles around circles around the Earth.


OK.

I take, like Deutsch, the two slits experiences (with photon or  
electrons, in a corresponding set-up, sent one by one) as a strong  
evidence of the Many Worlds/Dreams (MW). Then I take Aspect  
experience, and Bell's inequality violation testing as an even much  
stronger evidence for them. In fact all evidences for literal quantum  
mechanics are evidences for MW.


Bruno





 John K Clark





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Re: A thought on MWI and its alternative(s)

[Brent Meeker]

6/13/2017 4:11 AM, Telmo Menezes wrote:


The reason why it would follow is precisely the point of my rhetorical
question above. If you take the wave function seriously, then you take
seriously that qubits really do exist in a superposition of states,
and this explains the exponential increase in computational power as
you add qubits to the systems in certain configurations. I guess you
can accept superposition and deny many worlds, but I would say that it
is quite an awkward move.


Being in a superposition is just a matter choosing the basis.  If it's a
pure state then there's some basis in which it is not a superposition.
And if it's not in a superposition, then you can choose another basis in
which it is.

Brent

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

You seem to be taking the older view of many worlds that is favoured by 
David Deutsch. This approach has serious problems with the notorious 
basis problem, and there does not seem to be any principled way from 
within the theory to select unambiguosly the basis in which all of these 
worlds form. More recent understandings of MWI take decoherence into 
account. Decoherence provides a principled dynamical way to solve the 
basis problem, but it means the worlds do not actually form until there 
is decoherence -- worlds cannot form until they know what basis is relevant!


I recommend the paper I suggested to Telmo:

Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

Cuffaro discusses the problems with the older form of MWI and suggests 
that although many worlds might be a useful heuristic in quantum 
computing, decoherence is required before worlds could be considered to 
have any ontological basis. The exponential speedup with a quantum 
computer is then seen in the fact that the QC manipulates the phases 
inherent in the entanglement of qbits, and doesn't have to actually 
calculate the function in question for all possible inputs, as the older 
many worlds view requires.


Bruce



On 14/06/2017 4:09 am, John Clark wrote:
On Mon, Jun 12, 2017 at 8:32 PM, Bruce Kellett 
mailto:bhkell...@optusnet.com.au>>wrote:


​ >> ​
​I agree Interference must take place in a single world, but
where did all the information that produced the interference
come from, where did the computations that produced all those
wrong answers (and a few correct ones) come from?


​ > ​
What calculations are performed in these parallel worlds?


​Whatever algorithm you and your ​doppelgangers decided to run on 
their quantum computer.


​ > ​
And what performs those calculations?


​Computers made of matter that obey the laws of physics.

​ > ​
You are the one who insists that calculation is possible only on a
physical computer.


​Yes, but you almost make that sound as if it were a contradiction of 
some sort.


​ > ​
Who constructed all these physical computers in the parallel worlds?


​If the MWI is correct and if you're a computer engineer then ​
you and your ​doppelganger
​ s​
​ made the quantum computer, made lots and lots of them actually.

​ >> ​
Even the 2-slit experiment will not produce interference if
you remove the photographic plate and just allow the photons
to continue into infinite space after they pass the slits
because then the world splits but the two never recombine
again so no interference.


​ > ​
Of course the interference continues -- for ever if necessary. The
screen or photographic plate is only there to enable you to see it.


​No, in the ​Many World's theory it doesn't matter if anybody sees the 
results, in fact a brick wall would work just as well as a screen or a 
photographic plate, the only thing the MWI is interested in is that 
all of those things destroy the photon.


After the photon passed the slits that photon was the only difference 
between those 2 universes, when it is destroyed in both universes by a 
screen or photographic plate or brick wall there is no longer a 
difference between universes so they merge back together, 
but indications it went through slot A and indications it went through 
slot B remain. And that produces the interference pattern. We don't 
usually see this weird quantum effect in our everyday macro-world 
because when a large change is made between universes it's hard to 
arrange things so they evolve together toward the same point, become 
the identical again, and thus merge back together. That's why making a 
quantum computer is hard.



​ > ​
Of course the interference continues -- for ever if necessary.
​  [...] ​
Try moving the position of the screen, what happens?


​What happens is if you remove the ​
screen or photographic plate or brick wall
​ and just let the photon ​continue on into infinite space then 
*NON*-interference will continue forever because the 2 universes will 
always remain different and thus never recombine.

​
In the MWI the rules are crystal clear about when things split and 
when things merge back together. And In MWI

​ ​
everything that can happen does happen, so when a photon approaches 2 
slits the universe splits and one

​ ​
photon goes through the right slit and one goes through the left slit.
​ After
​ those 2​
​
photon
​ s​
hit
​ ​
a photographic plate
​ or screen ​
or a brick wall
​ the​
 photons no longer exist in either universe and so they merge back 
together into one universe

​ ,​
and this merger causes the interference lines. If instead
​ ,​
after passing the slits there is no photographic plate or
​ screen or ​
brick wall and the photons
​ ​
are allowed to continue on into infinite space then the 2 universes 
remain different and remain separated forever.

​ And so no inte

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 11 Jun 2017, at 19:07, David Nyman wrote:




On 11 Jun 2017 16:44, "Bruno Marchal"  wrote:

On 11 Jun 2017, at 12:24, David Nyman wrote:


On 11 June 2017 at 10:14, Bruno Marchal  wrote:

On 09 Jun 2017, at 20:21, David Nyman wrote:


On 9 June 2017 at 12:34, Bruno Marchal  wrote:

On 08 Jun 2017, at 02:05, Bruce Kellett wrote:

On 7/06/2017 10:38 pm, Bruno Marchal wrote:
On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
On 7/06/2017 7:09 pm, Bruno Marchal wrote:
On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome  
notation, but I will attempt to simplify as far as is possible. I  
will use '+' and '-' as spin states, rather than his 'left',  
'right'.


He write the initial wave function as for the case when you and I  
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
  = |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and  
neither observer is split. But his fundamental mistake is already  
present.


A little test for you: what is wrong with the above set of  
equations from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-]  
means you have measured '-'.


He then claims that the QM results of perfect anticorrelation in  
the case of parallel polarizers has been recovered without any non- 
local interaction!


Spoiler -- in order to write the final line for |psi_1> he has  
already assumed collapse, when I measure '+', you are presented  
*only* with '-', so of course you get the right result -- he has  
built that non-locality in from the start.


?

From the start shows that it is local.

Your failure to see the problem here is symptomatic of your  
complete failure to understand EPR in the MWI.


I could say the same, but emphatic statements are not helping. My  
feeling is that you interpret the singlet state above like if it  
prepares Alice and Bob particles in the respective + and - states,  
but that is not the case. The singlet state describe a multiverse  
where Alice and Bob have all possible states, yet correlated.


The singlet state is rotationally invariant, yes, and can be  
expanded in any basis of the 2-d complex Hilbert space. That has  
never been in doubt.


OK.



Then in absence of collapse, all interactions, and results are  
obtained locally, and does not need to be correlated until they  
spread at low speed up their partners.


That does not follow. Although there are an infinity of possible  
bases for the singlet state, these are potential only,


I don't understand this. Potential? That is no more the MW.





and do not exist in any operative sense until the state interacts  
with something that sets a direction.


That looks more like Bohr than Everett.




You appear to claim that A and B exist in separate worlds  
corresponding to each of this infinity of bases.


Yes. It is the rotaional invariance of the singlet states "taken  
seriously" when we drop the idea of collapse, or of special  
dualism between observer and the observed.





But that is a misunderstanding. They are in superpositions in  
every base, sure, but that does not mean that there are 'worlds'  
corresponding to each possible base until some external  
interaction occurs.


This is even more fuzzy than the collapse. It looks like  
consciousness not only reduce the wave, but create the physical  
reality. That is correct in Mechanism, but that is another story.




As you yourself have said, a world is something that is closed to  
interaction. But superpositions are not closed to interaction,  
they can interfere -- as in the two slit experiment, and  
essentially every other application of QM.


Right.



So there are no separate worlds corresponding to every possible  
orientation of the polarizers. Worlds can arise only after  
interaction and decoherence has progressed so that the overlap  
between the branches of the superposition is zero (FAPP if you  
like). It is only then that the branches can no longer interfere  
(interact) and are closed to interaction, and thus constitute  
different worlds.


We will have to disagree with this. I use the Y=II rules, like  
Deutsch. In this case the reading of the singlet state gives  
2^aleph_zero constantly spreading histories figuring Bob and  
Alice. With mechanism, those worlds/histories are more like  
dreams. They will be epistemological personal (and plural in the  
spreading interaction based spheres).





The standard procedure in quantum mechanics when one is faced with  
a superposition that interacts with something external, is to  
expand the superposition in a base that corresponds to the  
external context.


OK. In this case, A

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 13/06/2017 9:11 pm, Telmo Menezes wrote:

On Mon, Jun 12, 2017 at 3:43 AM, Bruce Kellett
 wrote:

On 11/06/2017 1:31 am, Telmo Menezes wrote:

I think you built a straw man and now you're attacking it. When I
heard Deutsch make the argument, he was referring explicitly to Shor's
algorithm. This is sufficient to demonstrate an increase in
computational power that would be impossible in the classical world.

No one is denying that Shor's algorithm on a quantum computer would
factorize numbers exponentially faster that a classical Turing machine could
do it. But that does not mean that a quantum computer is just  lot of
classical Turing machines acting in parallel.

No, but it does mean that a quantum computer can have the
computational power of a lot of Turing machines acting in parallel,
and it is normal to ask "why?", and be unsatisfied with a theory that
does not answer this question.


I have come across an interesting paper that discusses these questions, 
and comes to the conclusion that it is problematic to see quantum 
computing as accessing the computing power of other worlds.


Michael Cuffaro, http://arxiv.org/abs/1110.2514v2

The explanation for exponential speedup is:
"On this view, quantum computers are faster than classical computers 
because they perform /fewer/, not more, computations. By means of 
entanglement, quantum computers make it possible to manipulate the 
correlations present between the logical elements of a computation 
without representing these elements themselves.far from computing 
all of the values of a function simultaneously, quantum computers are 
faster because they avoid the calculation of any values of the function 
whatsoever, this time by exploiting the difference between classical and 
quantum logic."


I find that to be a quite satisfying explanation of quantum computer 
speedup.





I don't see how that could follow. The wave function exists in complex
configuration space -- that is not the "real world".

Well, I'm no sure about that, but classical mechanics exists in R^3
configuration space that is demonstrably not the real world (although
it is the model that most closely matches our day-to-day perception of
reality).


Actually, it is more usual to say that classical physics exists in 
6N-dimensional phase space for N particles. But that relates directly to 
positions and momenta in ordinary 3-space.



The reason why it would follow is precisely the point of my rhetorical
question above. If you take the wave function seriously, then you take
seriously that qubits really do exist in a superposition of states,
and this explains the exponential increase in computational power as
you add qubits to the systems in certain configurations. I guess you
can accept superposition and deny many worlds, but I would say that it
is quite an awkward move.


Cuffaro argues that many worlds can be a useful heuristic for certain 
types of quantum algorithms, but that reifying the elements of 
superpositons as defining different 'worlds' runs into difficulty with 
the basis problem.



In other posts you alluded to a purely probabilistic interpretation of
quantum mechanics. In that case, I would say that it also becomes
awkward to explain the exponential increase in computational power for
the quantum Fourier transform. These are all just intuitions, of
course. We all have ours.


Not really difficult to explain if you look at in the right way. See above.


Another problem for me with the purely probabilistic interpretation is
that it gives base-level reality to true randomness, and that would
also be quite mysterious in my view. My point being: you argue as if
probabilistic interpretations remove weirdness from the explanation,
but for me true randomness is weirder than many worlds.


Well, we all have our intuitions, as you say. If it is the case that 
there is an objective collapse mechanism, as in Bohm's theory, Ghirardi 
et al, or Penrose and others, then there is base level randomness and we 
just have to get used to it. Intuitions developed in a deterministic 
classical world do not necessarily carry across into the quantum realm.


Bruce

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Re: A thought on MWI and its alternative(s)

[John Clark]

On Mon, Jun 12, 2017 at 8:32 PM, Bruce Kellett 
wrote:

​>> ​
>> ​I agree Interference must take place in a single world, but where did
>> all the information that produced the interference come from, where did the
>> computations that produced all those wrong answers (and a few correct ones)
>> come from?
>
>
> ​> ​
> What calculations are performed in these parallel worlds?
>

​Whatever algorithm you and your ​doppelgangers decided to run on their
quantum computer.


> ​> ​
> And what performs those calculations?
>

​Computers made of matter that obey the laws of physics.


> ​> ​
> You are the one who insists that calculation is possible only on a
> physical computer.
>

​Yes, but you almost make that sound as if it were a contradiction of some
sort.


> ​> ​
> Who constructed all these physical computers in the parallel worlds?
>

​If the MWI is correct and if you're a computer engineer then ​
you and your ​doppelganger
​s​

​made the quantum computer, made lots and lots of them actually.


> ​>> ​
>> Even the 2-slit experiment will not produce interference if you remove
>> the photographic plate and just allow the photons to continue into infinite
>> space after they pass the slits because then the world splits but the two
>> never recombine again so no interference.
>
>
> ​> ​
> Of course the interference continues -- for ever if necessary. The screen
> or photographic plate is only there to enable you to see it.
>

​No, in the ​Many World's theory it doesn't matter if anybody sees the
results, in fact a brick wall would work just as well as a screen or a
photographic plate, the only thing the MWI is interested in is that all of
those things destroy the photon.

After the photon passed the slits that photon was the only difference
between those 2 universes, when it is destroyed in both universes by a screen
or photographic plate or brick wall there is no longer a difference between
universes so they merge back together, but indications it went through slot
A and indications it went through slot B remain. And that produces the
interference pattern. We don't usually see this weird quantum effect in our
everyday macro-world because when a large change is made between universes
it's hard to arrange things so they evolve together toward the same point,
become the identical again, and thus merge back together. That's why making
a quantum computer is hard.



> ​> ​
> Of course the interference continues -- for ever if necessary.
> ​  [...] ​
> Try moving the position of the screen, what happens?


​What happens is if you remove the ​
screen or photographic plate or brick wall
​ and just let the photon ​continue on into infinite space then
*NON*-interference
will continue forever because the 2 universes will always remain different
and thus never recombine.

​
In the MWI the rules are crystal clear about when things split and when
things merge back together. And In MWI
​ ​
everything that can happen does happen, so when a photon approaches 2 slits
the universe splits and one
​​
photon goes through the right slit and one goes through the left slit.
​After

​those 2​
​
photon
​s​
hit
​​
a photographic plate
​or screen ​
or a brick wall
​the​
 photons no longer exist in either universe and so they merge back together
into one universe
​,​
and this merger causes the interference lines. If instead
​,​
after passing the slits there is no photographic plate or
​screen or ​
brick wall and the photons
​ ​
are allowed to continue on into infinite space then the 2 universes remain
different and remain separated forever.
​ And so no interference between them ever occurs.

​> ​
> Superpositions occur everywhere, and no new worlds are split off until
> there is decoherence.


But we don't ALWAYS see a superposition of states. You can place a detector
next
​to ​
one of the slits so you you know which slit each photon went through, but
if you do that the interference pattern disappears because interference
needs at least 2 different things to interferer with and with this modified
experiment
​ ​
the universe doesn't split so it can't recombine so you see no interference
pattern. In the unmodified
​ ​
experiment
​ ​
after the photon makes its decision on
​ ​
which of the 2 slits to go through
​ i​
t then hits a
​ ​
screen or
​ ​
photographic plate or brick wall. When that happens
​ ​the
 photons in
​ ​
both universes are destroyed and thus there is no longer any difference
​ ​
between the two, so the universes will merge back together. T
​hen​
you will
​ ​
see a superposition of states. Then you will see indications that you live
​ ​
in a universe where the photon went through slot A only and indications
​ ​
you live in a universe where the photon went through slot B only,
​ ​
and that is why you see an interference effect even if you only send one
​ ​
photon at a time at the slits.
​ ​
If you got rid of the film (or the brick wall) and let the photon head out
​ ​
into infinite space after it passed the slits then the unive

Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

On Mon, Jun 12, 2017 at 3:43 AM, Bruce Kellett
 wrote:
> On 11/06/2017 1:31 am, Telmo Menezes wrote:
>>
>> On Sat, Jun 10, 2017 at 1:11 AM, Bruce Kellett
>>  wrote:
>>>
>>> On 10/06/2017 2:36 am, Telmo Menezes wrote:

 On Fri, Jun 9, 2017 at 12:37 AM, Bruce Kellett

> The idea that the explanation is epistemological rather that
> ontological
> has
> been my preferred position for a long time. If the wave-function is
> merely
> an epistemological device for calculating probabilities and not a
> really
> existing object, all worries about collapse and action-at-a-distance
> vanish.
> Of course, multi worlds also vanish, but in my opinion that is no bad
> thing.

 So what's your position on Deutsch's argument about quantum computers?
 Where does the extra computing power come from?
>>>
>>>
>>> It has long been understood that Deutsch is out to lunch on this.
>>>
>>> He appears
>>> to assume that a quantum computer is just using the same algorithms that
>>> a
>>> classical computer would use, only executing them in a massively parallel
>>> manner.
>>
>> I find it very hard to believe that David Deutsch does not have a good
>> understanding of quantum computers.
>>
>>> This is manifestly false. Quantum computers operate in a completely
>>> different way -- that is why there are so few actual algorithms for
>>> quantum
>>> computers to execute that gain massive speed improvements.
>>
>> I think you built a straw man and now you're attacking it. When I
>> heard Deutsch make the argument, he was referring explicitly to Shor's
>> algorithm. This is sufficient to demonstrate an increase in
>> computational power that would be impossible in the classical world.
>
>
> No one is denying that Shor's algorithm on a quantum computer would
> factorize numbers exponentially faster that a classical Turing machine could
> do it. But that does not mean that a quantum computer is just  lot of
> classical Turing machines acting in parallel.

No, but it does mean that a quantum computer can have the
computational power of a lot of Turing machines acting in parallel,
and it is normal to ask "why?", and be unsatisfied with a theory that
does not answer this question.

>> As for more general speed improvements, there is for example Grover's
>> algorithm, that offers a quadratic improvement in searching unsorted
>> lists. This has wide applicability in software engineering.
>>
>> Of course, building more complex quantum computers is still beyond our
>> technical abilities. I don't think that's news for anyone...
>>
>>> As Brent says in his recent post, Scott Aaronson points out:
>>> "The way a quantum algorithms work is that they arrange for wrong answers
>>> to
>>> destructively interfere while the desired answer interferes
>>> constructively.
>>> Interference requires that they take place in the same world."
>>
>> Yes, but this is not classical interference, it's interference between
>> superpositions of states. So how can this computation happen in the
>> physical world?
>
>
> No one is suggesting that this is classical interference. Interference
> between superpositions of states does happen in the physical world!

Yes, this was a rhetorical question.

> Are you
> suggesting that two-slit interference does not happen in the physical world?
> Interference between qbits happens in the physical world just as much as
> two-slit interference. If you define a "world" as something closed to
> outside interactions, then interference can only take place in the one
> world.
>
>>   For me, that gives more credence to the claim that the
>> wave function describes a real object.
>
>
> I don't see how that could follow. The wave function exists in complex
> configuration space -- that is not the "real world".

Well, I'm no sure about that, but classical mechanics exists in R^3
configuration space that is demonstrably not the real world (although
it is the model that most closely matches our day-to-day perception of
reality).

The reason why it would follow is precisely the point of my rhetorical
question above. If you take the wave function seriously, then you take
seriously that qubits really do exist in a superposition of states,
and this explains the exponential increase in computational power as
you add qubits to the systems in certain configurations. I guess you
can accept superposition and deny many worlds, but I would say that it
is quite an awkward move.

In other posts you alluded to a purely probabilistic interpretation of
quantum mechanics. In that case, I would say that it also becomes
awkward to explain the exponential increase in computational power for
the quantum Fourier transform. These are all just intuitions, of
course. We all have ours.

Another problem for me with the purely probabilistic interpretation is
that it gives base-level reality to true randomness, and that would
also be quite mysterious in my view. My point being: you argue as if
probabilistic i

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 13/06/2017 1:09 am, John Clark wrote:
On Fri, Jun 9, 2017 at 7:11 PM, Bruce Kellett 
mailto:bhkell...@optusnet.com.au>>wrote:


​ >
Scott Aaronson points out:
"/The way a quantum algorithms work is that they arrange for wrong
answers to destructively interfere while the desired answer
interferes constructively. Interference requires that they take
place in the same world/."


​I agree Interference must take place in a single world, but where did 
all the information that produced the interference come from, where 
did the computations that produced all those wrong answers (and a few 
correct ones) come from?


What calculations are performed in these parallel worlds? And what 
performs those calculations? You are the one who insists that 
calculation is possible only on a physical computer. Who constructed all 
these physical computers in the parallel worlds?


Even the 2-slit experiment will not produce interference if you remove 
the photographic plate and just allow the photons to continue into 
infinite space after they pass the slits because then the world splits 
but the two never recombine again so no interference.


Of course the interference continues -- for ever if necessary. The 
screen or photographic plate is only there to enable you to see it. Try 
moving the position of the screen, what happens?


You need places for things to become different and also a place for 
things to come together again for interference to occur.


Superpositions occur everywhere, and no new worlds are split off until 
there is decoherence.


Bruce

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Re: A thought on MWI and its alternative(s)

[John Clark]

On Fri, Jun 9, 2017 at 7:11 PM, Bruce Kellett 
wrote:

​> ​
> Deutsch is out to lunch on this. He appears to assume that a quantum
> computer is just using the same algorithms that a classical computer would
> use, only executing them in a massively parallel manner.


​As Deutsch is ​probably only the second person (after Richard Feynman) to
think long and hard about quantum computers I'm pretty sure he doesn't
believe that just any old algorithm will do, and I'm even more sure he
doesn't believe the classical hardware we use in our computers today can
take advantage of a quantum speedup.


> ​>
> Scott Aaronson points out:
> "*The way a quantum algorithms work is that they arrange for wrong
> answers to destructively interfere while the desired answer interferes
> constructively. Interference requires that they take place in the same
> world*."


​I agree Interference must take place in a single world, but where did all
the information that produced the interference come from, where did the
computations that produced all those wrong answers (and a few correct ones)
come from? Even the 2-slit experiment will not produce interference if you
remove the photographic plate and just allow the photons to continue into
infinite space after they pass the slits because then the world splits but
the two never recombine again so no interference. You need places for
things to become different and also a place for things to come together
again for interference to occur.

​>
> Quantum computing does not prove the existence of parallel worlds -- there
> is no need for other worlds in which to find the computational power,


​
A large Quantum Computer wouldn't prove beyond any logical doubt that other
world's must exist, but then you don't exactly "need" a
​ ​
heliocentric
​ ​
solar system theory to explain the movements of the planets either;
​ ​
you could stick with the Earth centered model if you added enough epicycles
of the type used by Ptolemy 2000 years ago
​.​

​T​
hen the way the planets moved in relation to the crystalline celestial
sphere
​,​
​ ​the one
that
​has ​
the stars painted on
​ it, ​
could be
​ ​
predicted
​ ​
to the limits
​ ​
of observational accuracy. But you'd need a awful lot of
​ ​
epicycles and calculations would literally
​be ​
astronomically more complex than with the
​ ​
far simpler
​ ​
heliocentric
​ ​
model.

In the same way I think when quantum computers become commonplace
programers will
​take ​
Many Worlds as a given even if they
​can't​
 formally prove they exist because it's just easier to visualize how they
work that way, just as it's easier to visualize a few elliptical orbit
​s​
around the sun than
​ ​visualize a
gazilian
​ ​circles around circles around circles around the Earth.

 John K Clark

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 11/06/2017 7:14 pm, Bruno Marchal wrote:

On 09 Jun 2017, at 20:21, David Nyman wrote:
On 9 June 2017 at 12:34, Bruno Marchal > wrote:




OK. In this case, Alice choose to measure her spin. This will
only self-localized here in one (actually still aleph_0)
histories, where she will know her states, and the states of any
Bob she could soon or later interact with, but not of the
inaccessible Bobs, who might found non correlated result. yet,n
him too will be able to met only the Alice(s) having the
correlated spin.


​Why?


That is due to the singlet state.  [Alice Bob ( up down - down up) ]= 
[Alice Bob up down - Alice Bob down up] keeps its rotational symmetry, 
even after the interaction took place.


That is false. The measurement of a spin or polarization state 
introduces an externally defined direction that destroys the rotational 
symmetry of the original state. And in general, Alice and Bob will 
introduce different external directions.


The correlation are built in by the preparation of that state, and is 
valide whatever the smpin direction are, so you can add prime to up 
and down, for the other direction, and the correlation does not 
depends on the base, and evolve locally.


The rotational symmetry does not depend on the basis, but it does not 
evolve locally since the particles move apart and no longer interact.


When space separated, they are independent, but by virtue of the 
singlet state, if they do measurement, they will put themselves in 
"independent" and possible different superposition, which will 
'contagiate' their respective environment up to *different* partners 
who will get the right correlation by the math of the singlet state 
which will not allow any Alice and Bob to not confirm the singlet , 
highly correlated state.


That is just an appeal to magic.

The singlet state describe an infinity of Alice and Bob, having all 
their spin being correlated,


No, it does not. There is only one Alice and Bob -- it is only the 
direction in which they choose to measure the spin/polarization that is 
undefined until they actually do it. Then they can only each split into 
two copies in the case under discussion.


and they localoze themselves in which one when doing measurement. This 
can be used to show that they will conclude that Bell's inequality is 
violated, despite no influence at a distance exist. There is only 
spreading superposition, and all Alice and Bob can only meet their 
corresponding partners.


Sure, they can only meet their corresponding partners, but how do they 
know, in your account, which partners correspond?


Bruce

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 11/06/2017 1:31 am, Telmo Menezes wrote:

On Sat, Jun 10, 2017 at 1:11 AM, Bruce Kellett
 wrote:

On 10/06/2017 2:36 am, Telmo Menezes wrote:

On Fri, Jun 9, 2017 at 12:37 AM, Bruce Kellett


The idea that the explanation is epistemological rather that ontological
has
been my preferred position for a long time. If the wave-function is
merely
an epistemological device for calculating probabilities and not a really
existing object, all worries about collapse and action-at-a-distance
vanish.
Of course, multi worlds also vanish, but in my opinion that is no bad
thing.

So what's your position on Deutsch's argument about quantum computers?
Where does the extra computing power come from?


It has long been understood that Deutsch is out to lunch on this.

He appears
to assume that a quantum computer is just using the same algorithms that a
classical computer would use, only executing them in a massively parallel
manner.

I find it very hard to believe that David Deutsch does not have a good
understanding of quantum computers.


This is manifestly false. Quantum computers operate in a completely
different way -- that is why there are so few actual algorithms for quantum
computers to execute that gain massive speed improvements.

I think you built a straw man and now you're attacking it. When I
heard Deutsch make the argument, he was referring explicitly to Shor's
algorithm. This is sufficient to demonstrate an increase in
computational power that would be impossible in the classical world.


No one is denying that Shor's algorithm on a quantum computer would 
factorize numbers exponentially faster that a classical Turing machine 
could do it. But that does not mean that a quantum computer is just  lot 
of classical Turing machines acting in parallel.



As for more general speed improvements, there is for example Grover's
algorithm, that offers a quadratic improvement in searching unsorted
lists. This has wide applicability in software engineering.

Of course, building more complex quantum computers is still beyond our
technical abilities. I don't think that's news for anyone...


As Brent says in his recent post, Scott Aaronson points out:
"The way a quantum algorithms work is that they arrange for wrong answers to
destructively interfere while the desired answer interferes constructively.
Interference requires that they take place in the same world."

Yes, but this is not classical interference, it's interference between
superpositions of states. So how can this computation happen in the
physical world?


No one is suggesting that this is classical interference. Interference 
between superpositions of states does happen in the physical world! Are 
you suggesting that two-slit interference does not happen in the 
physical world? Interference between qbits happens in the physical world 
just as much as two-slit interference. If you define a "world" as 
something closed to outside interactions, then interference can only 
take place in the one world.



  For me, that gives more credence to the claim that the
wave function describes a real object.


I don't see how that could follow. The wave function exists in complex 
configuration space -- that is not the "real world".



Classical computers do not have quantum interference. Quantum computing does
not prove the existence of parallel worlds -- there is no need for other
worlds in which to find the computational power, you just need a modicum of
insight into how quantum computing algorithms work.

You might claim that Deutsch is a known expert on quantum computing, but
more commonly, Deutsch is known for having way out, non-standard ideas on
quantum mechanics.

Oh no! Everyone should be kept in line!


Physics is full of people who take non-standard positions. On the whole, 
that is a good thing, because it provides an opportunity for real 
advances in understanding. But that does not mean that all non-standard 
positions are 'true' or valuable.


Bruce

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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 11 Jun 2017 16:44, "Bruno Marchal"  wrote:


On 11 Jun 2017, at 12:24, David Nyman wrote:

On 11 June 2017 at 10:14, Bruno Marchal  wrote:

>
> On 09 Jun 2017, at 20:21, David Nyman wrote:
>
> On 9 June 2017 at 12:34, Bruno Marchal  wrote:
>
>>
>> On 08 Jun 2017, at 02:05, Bruce Kellett wrote:
>>
>> On 7/06/2017 10:38 pm, Bruno Marchal wrote:
>>>
 On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
 On 7/06/2017 7:09 pm, Bruno Marchal wrote:

> On 06 Jun 2017, at 01:23, Bruce Kellett wrote:
>>
>> I have been through this before. I looked at Price again this morning
>>> and was frankly appalled at the stupidity of what I saw.
>>> Let me summarize briefly what he did. He has a very cumbersome
>>> notation, but I will attempt to simplify as far as is possible. I will 
>>> use
>>> '+' and '-' as spin states, rather than his 'left', 'right'.
>>>
>>> He write the initial wave function as for the case when you and I
>>> agree in advance to have aligned polarizers:
>>>
>>> |psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
>>>   = |me, +,-,you> - |me,-,+,you>
>>>
>>> He says that at this point no measurements have been made, and
>>> neither observer is split. But his fundamental mistake is already 
>>> present.
>>>
>>> A little test for you: what is wrong with the above set of equations
>>> from a no-collapse pov?
>>>
>>> skipping some tedium, he then gets
>>>
>>> |psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>
>>>
>>> where the notation me[+] etc means I have measured '+', you[-] means
>>> you have measured '-'.
>>>
>>> He then claims that the QM results of perfect anticorrelation in the
>>> case of parallel polarizers has been recovered without any non-local
>>> interaction!
>>>
>>> Spoiler -- in order to write the final line for |psi_1> he has
>>> already assumed collapse, when I measure '+', you are presented *only* 
>>> with
>>> '-', so of course you get the right result -- he has built that
>>> non-locality in from the start.
>>>
>>
>> ?
>>
>> From the start shows that it is local.
>>
>
> Your failure to see the problem here is symptomatic of your complete
> failure to understand EPR in the MWI.
>

 I could say the same, but emphatic statements are not helping. My
 feeling is that you interpret the singlet state above like if it prepares
 Alice and Bob particles in the respective + and - states, but that is not
 the case. The singlet state describe a multiverse where Alice and Bob have
 all possible states, yet correlated.

>>>
>>> The singlet state is rotationally invariant, yes, and can be expanded in
>>> any basis of the 2-d complex Hilbert space. That has never been in doubt.
>>>
>>
>> OK.
>>
>>
>>
>>> Then in absence of collapse, all interactions, and results are obtained
 locally, and does not need to be correlated until they spread at low speed
 up their partners.

>>>
>>> That does not follow. Although there are an infinity of possible bases
>>> for the singlet state, these are potential only,
>>>
>>
>> I don't understand this. Potential? That is no more the MW.
>>
>>
>>
>>
>>
>> and do not exist in any operative sense until the state interacts with
>>> something that sets a direction.
>>>
>>
>> That looks more like Bohr than Everett.
>>
>>
>>
>>
>> You appear to claim that A and B exist in separate worlds corresponding
>>> to each of this infinity of bases.
>>>
>>
>> Yes. It is the rotaional invariance of the singlet states "taken
>> seriously" when we drop the idea of collapse, or of special dualism between
>> observer and the observed.
>>
>>
>>
>>
>> But that is a misunderstanding. They are in superpositions in every base,
>>> sure, but that does not mean that there are 'worlds' corresponding to each
>>> possible base until some external interaction occurs.
>>>
>>
>> This is even more fuzzy than the collapse. It looks like consciousness
>> not only reduce the wave, but create the physical reality. That is correct
>> in Mechanism, but that is another story.
>>
>>
>>
>> As you yourself have said, a world is something that is closed to
>>> interaction. But superpositions are not closed to interaction, they can
>>> interfere -- as in the two slit experiment, and essentially every other
>>> application of QM.
>>>
>>
>> Right.
>>
>>
>>
>>> So there are no separate worlds corresponding to every possible
>>> orientation of the polarizers. Worlds can arise only after interaction and
>>> decoherence has progressed so that the overlap between the branches of the
>>> superposition is zero (FAPP if you like). It is only then that the branches
>>> can no longer interfere (interact) and are closed to interaction, and thus
>>> constitute different worlds.
>>>
>>
>> We will have to disagree with this. I use the Y=II rules, like Deutsch.
>> In this case the readin

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 11 Jun 2017, at 12:24, David Nyman wrote:


On 11 June 2017 at 10:14, Bruno Marchal  wrote:

On 09 Jun 2017, at 20:21, David Nyman wrote:


On 9 June 2017 at 12:34, Bruno Marchal  wrote:

On 08 Jun 2017, at 02:05, Bruce Kellett wrote:

On 7/06/2017 10:38 pm, Bruno Marchal wrote:
On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
On 7/06/2017 7:09 pm, Bruno Marchal wrote:
On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome  
notation, but I will attempt to simplify as far as is possible. I  
will use '+' and '-' as spin states, rather than his 'left', 'right'.


He write the initial wave function as for the case when you and I  
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
  = |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and  
neither observer is split. But his fundamental mistake is already  
present.


A little test for you: what is wrong with the above set of  
equations from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-]  
means you have measured '-'.


He then claims that the QM results of perfect anticorrelation in  
the case of parallel polarizers has been recovered without any non- 
local interaction!


Spoiler -- in order to write the final line for |psi_1> he has  
already assumed collapse, when I measure '+', you are presented  
*only* with '-', so of course you get the right result -- he has  
built that non-locality in from the start.


?

From the start shows that it is local.

Your failure to see the problem here is symptomatic of your  
complete failure to understand EPR in the MWI.


I could say the same, but emphatic statements are not helping. My  
feeling is that you interpret the singlet state above like if it  
prepares Alice and Bob particles in the respective + and - states,  
but that is not the case. The singlet state describe a multiverse  
where Alice and Bob have all possible states, yet correlated.


The singlet state is rotationally invariant, yes, and can be  
expanded in any basis of the 2-d complex Hilbert space. That has  
never been in doubt.


OK.



Then in absence of collapse, all interactions, and results are  
obtained locally, and does not need to be correlated until they  
spread at low speed up their partners.


That does not follow. Although there are an infinity of possible  
bases for the singlet state, these are potential only,


I don't understand this. Potential? That is no more the MW.





and do not exist in any operative sense until the state interacts  
with something that sets a direction.


That looks more like Bohr than Everett.




You appear to claim that A and B exist in separate worlds  
corresponding to each of this infinity of bases.


Yes. It is the rotaional invariance of the singlet states "taken  
seriously" when we drop the idea of collapse, or of special dualism  
between observer and the observed.





But that is a misunderstanding. They are in superpositions in every  
base, sure, but that does not mean that there are 'worlds'  
corresponding to each possible base until some external interaction  
occurs.


This is even more fuzzy than the collapse. It looks like  
consciousness not only reduce the wave, but create the physical  
reality. That is correct in Mechanism, but that is another story.




As you yourself have said, a world is something that is closed to  
interaction. But superpositions are not closed to interaction, they  
can interfere -- as in the two slit experiment, and essentially  
every other application of QM.


Right.



So there are no separate worlds corresponding to every possible  
orientation of the polarizers. Worlds can arise only after  
interaction and decoherence has progressed so that the overlap  
between the branches of the superposition is zero (FAPP if you  
like). It is only then that the branches can no longer interfere  
(interact) and are closed to interaction, and thus constitute  
different worlds.


We will have to disagree with this. I use the Y=II rules, like  
Deutsch. In this case the reading of the singlet state gives  
2^aleph_zero constantly spreading histories figuring Bob and Alice.  
With mechanism, those worlds/histories are more like dreams. They  
will be epistemological personal (and plural in the spreading  
interaction based spheres).





The standard procedure in quantum mechanics when one is faced with  
a superposition that interacts with something external, is to  
expand the superposition in a base that corresponds to the external  
context.


OK. In this case, Alice choose to measure her spin. This will only  
self-localized here in one (actually still aleph

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 11 June 2017 at 10:14, Bruno Marchal  wrote:

>
> On 09 Jun 2017, at 20:21, David Nyman wrote:
>
> On 9 June 2017 at 12:34, Bruno Marchal  wrote:
>
>>
>> On 08 Jun 2017, at 02:05, Bruce Kellett wrote:
>>
>> On 7/06/2017 10:38 pm, Bruno Marchal wrote:
>>>
 On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
 On 7/06/2017 7:09 pm, Bruno Marchal wrote:

> On 06 Jun 2017, at 01:23, Bruce Kellett wrote:
>>
>> I have been through this before. I looked at Price again this morning
>>> and was frankly appalled at the stupidity of what I saw.
>>> Let me summarize briefly what he did. He has a very cumbersome
>>> notation, but I will attempt to simplify as far as is possible. I will 
>>> use
>>> '+' and '-' as spin states, rather than his 'left', 'right'.
>>>
>>> He write the initial wave function as for the case when you and I
>>> agree in advance to have aligned polarizers:
>>>
>>> |psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
>>>   = |me, +,-,you> - |me,-,+,you>
>>>
>>> He says that at this point no measurements have been made, and
>>> neither observer is split. But his fundamental mistake is already 
>>> present.
>>>
>>> A little test for you: what is wrong with the above set of equations
>>> from a no-collapse pov?
>>>
>>> skipping some tedium, he then gets
>>>
>>> |psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>
>>>
>>> where the notation me[+] etc means I have measured '+', you[-] means
>>> you have measured '-'.
>>>
>>> He then claims that the QM results of perfect anticorrelation in the
>>> case of parallel polarizers has been recovered without any non-local
>>> interaction!
>>>
>>> Spoiler -- in order to write the final line for |psi_1> he has
>>> already assumed collapse, when I measure '+', you are presented *only* 
>>> with
>>> '-', so of course you get the right result -- he has built that
>>> non-locality in from the start.
>>>
>>
>> ?
>>
>> From the start shows that it is local.
>>
>
> Your failure to see the problem here is symptomatic of your complete
> failure to understand EPR in the MWI.
>

 I could say the same, but emphatic statements are not helping. My
 feeling is that you interpret the singlet state above like if it prepares
 Alice and Bob particles in the respective + and - states, but that is not
 the case. The singlet state describe a multiverse where Alice and Bob have
 all possible states, yet correlated.

>>>
>>> The singlet state is rotationally invariant, yes, and can be expanded in
>>> any basis of the 2-d complex Hilbert space. That has never been in doubt.
>>>
>>
>> OK.
>>
>>
>>
>>> Then in absence of collapse, all interactions, and results are obtained
 locally, and does not need to be correlated until they spread at low speed
 up their partners.

>>>
>>> That does not follow. Although there are an infinity of possible bases
>>> for the singlet state, these are potential only,
>>>
>>
>> I don't understand this. Potential? That is no more the MW.
>>
>>
>>
>>
>>
>> and do not exist in any operative sense until the state interacts with
>>> something that sets a direction.
>>>
>>
>> That looks more like Bohr than Everett.
>>
>>
>>
>>
>> You appear to claim that A and B exist in separate worlds corresponding
>>> to each of this infinity of bases.
>>>
>>
>> Yes. It is the rotaional invariance of the singlet states "taken
>> seriously" when we drop the idea of collapse, or of special dualism between
>> observer and the observed.
>>
>>
>>
>>
>> But that is a misunderstanding. They are in superpositions in every base,
>>> sure, but that does not mean that there are 'worlds' corresponding to each
>>> possible base until some external interaction occurs.
>>>
>>
>> This is even more fuzzy than the collapse. It looks like consciousness
>> not only reduce the wave, but create the physical reality. That is correct
>> in Mechanism, but that is another story.
>>
>>
>>
>> As you yourself have said, a world is something that is closed to
>>> interaction. But superpositions are not closed to interaction, they can
>>> interfere -- as in the two slit experiment, and essentially every other
>>> application of QM.
>>>
>>
>> Right.
>>
>>
>>
>>> So there are no separate worlds corresponding to every possible
>>> orientation of the polarizers. Worlds can arise only after interaction and
>>> decoherence has progressed so that the overlap between the branches of the
>>> superposition is zero (FAPP if you like). It is only then that the branches
>>> can no longer interfere (interact) and are closed to interaction, and thus
>>> constitute different worlds.
>>>
>>
>> We will have to disagree with this. I use the Y=II rules, like Deutsch.
>> In this case the reading of the singlet state gives 2^aleph_zero constantly
>> spreading histories figuring Bob and A

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 09 Jun 2017, at 20:21, David Nyman wrote:


On 9 June 2017 at 12:34, Bruno Marchal  wrote:

On 08 Jun 2017, at 02:05, Bruce Kellett wrote:

On 7/06/2017 10:38 pm, Bruno Marchal wrote:
On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
On 7/06/2017 7:09 pm, Bruno Marchal wrote:
On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome  
notation, but I will attempt to simplify as far as is possible. I  
will use '+' and '-' as spin states, rather than his 'left', 'right'.


He write the initial wave function as for the case when you and I  
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
  = |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and  
neither observer is split. But his fundamental mistake is already  
present.


A little test for you: what is wrong with the above set of equations  
from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-] means  
you have measured '-'.


He then claims that the QM results of perfect anticorrelation in the  
case of parallel polarizers has been recovered without any non-local  
interaction!


Spoiler -- in order to write the final line for |psi_1> he has  
already assumed collapse, when I measure '+', you are presented  
*only* with '-', so of course you get the right result -- he has  
built that non-locality in from the start.


?

From the start shows that it is local.

Your failure to see the problem here is symptomatic of your complete  
failure to understand EPR in the MWI.


I could say the same, but emphatic statements are not helping. My  
feeling is that you interpret the singlet state above like if it  
prepares Alice and Bob particles in the respective + and - states,  
but that is not the case. The singlet state describe a multiverse  
where Alice and Bob have all possible states, yet correlated.


The singlet state is rotationally invariant, yes, and can be  
expanded in any basis of the 2-d complex Hilbert space. That has  
never been in doubt.


OK.



Then in absence of collapse, all interactions, and results are  
obtained locally, and does not need to be correlated until they  
spread at low speed up their partners.


That does not follow. Although there are an infinity of possible  
bases for the singlet state, these are potential only,


I don't understand this. Potential? That is no more the MW.





and do not exist in any operative sense until the state interacts  
with something that sets a direction.


That looks more like Bohr than Everett.




You appear to claim that A and B exist in separate worlds  
corresponding to each of this infinity of bases.


Yes. It is the rotaional invariance of the singlet states "taken  
seriously" when we drop the idea of collapse, or of special dualism  
between observer and the observed.





But that is a misunderstanding. They are in superpositions in every  
base, sure, but that does not mean that there are 'worlds'  
corresponding to each possible base until some external interaction  
occurs.


This is even more fuzzy than the collapse. It looks like  
consciousness not only reduce the wave, but create the physical  
reality. That is correct in Mechanism, but that is another story.




As you yourself have said, a world is something that is closed to  
interaction. But superpositions are not closed to interaction, they  
can interfere -- as in the two slit experiment, and essentially  
every other application of QM.


Right.



So there are no separate worlds corresponding to every possible  
orientation of the polarizers. Worlds can arise only after  
interaction and decoherence has progressed so that the overlap  
between the branches of the superposition is zero (FAPP if you  
like). It is only then that the branches can no longer interfere  
(interact) and are closed to interaction, and thus constitute  
different worlds.


We will have to disagree with this. I use the Y=II rules, like  
Deutsch. In this case the reading of the singlet state gives  
2^aleph_zero constantly spreading histories figuring Bob and Alice.  
With mechanism, those worlds/histories are more like dreams. They  
will be epistemological personal (and plural in the spreading  
interaction based spheres).





The standard procedure in quantum mechanics when one is faced with a  
superposition that interacts with something external, is to expand  
the superposition in a base that corresponds to the external context.


OK. In this case, Alice choose to measure her spin. This will only  
self-localized here in one (actually still aleph_0) histories, where  
she will know her states, and the states of any Bob she could soon  
or lat

Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

On Sat, Jun 10, 2017 at 1:11 AM, Bruce Kellett
 wrote:
> On 10/06/2017 2:36 am, Telmo Menezes wrote:
>>
>> On Fri, Jun 9, 2017 at 12:37 AM, Bruce Kellett
>>
>>> The idea that the explanation is epistemological rather that ontological
>>> has
>>> been my preferred position for a long time. If the wave-function is
>>> merely
>>> an epistemological device for calculating probabilities and not a really
>>> existing object, all worries about collapse and action-at-a-distance
>>> vanish.
>>> Of course, multi worlds also vanish, but in my opinion that is no bad
>>> thing.
>>
>> So what's your position on Deutsch's argument about quantum computers?
>> Where does the extra computing power come from?
>
>
> It has long been understood that Deutsch is out to lunch on this.
>
> He appears
> to assume that a quantum computer is just using the same algorithms that a
> classical computer would use, only executing them in a massively parallel
> manner.

I find it very hard to believe that David Deutsch does not have a good
understanding of quantum computers.

> This is manifestly false. Quantum computers operate in a completely
> different way -- that is why there are so few actual algorithms for quantum
> computers to execute that gain massive speed improvements.

I think you built a straw man and now you're attacking it. When I
heard Deutsch make the argument, he was referring explicitly to Shor's
algorithm. This is sufficient to demonstrate an increase in
computational power that would be impossible in the classical world.

As for more general speed improvements, there is for example Grover's
algorithm, that offers a quadratic improvement in searching unsorted
lists. This has wide applicability in software engineering.

Of course, building more complex quantum computers is still beyond our
technical abilities. I don't think that's news for anyone...

> As Brent says in his recent post, Scott Aaronson points out:
> "The way a quantum algorithms work is that they arrange for wrong answers to
> destructively interfere while the desired answer interferes constructively.
> Interference requires that they take place in the same world."

Yes, but this is not classical interference, it's interference between
superpositions of states. So how can this computation happen in the
physical world? For me, that gives more credence to the claim that the
wave function describes a real object.

> Classical computers do not have quantum interference. Quantum computing does
> not prove the existence of parallel worlds -- there is no need for other
> worlds in which to find the computational power, you just need a modicum of
> insight into how quantum computing algorithms work.
>
> You might claim that Deutsch is a known expert on quantum computing, but
> more commonly, Deutsch is known for having way out, non-standard ideas on
> quantum mechanics.

Oh no! Everyone should be kept in line!

Telmo.

>
> Bruce
>
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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 10/06/2017 4:21 am, David Nyman wrote:
On 9 June 2017 at 12:34, Bruno Marchal > wrote:




OK. In this case, Alice choose to measure her spin. This will only
self-localized here in one (actually still aleph_0) histories,
where she will know her states, and the states of any Bob she
could soon or later interact with, but not of the inaccessible
Bobs, who might found non correlated result. yet,n him too will be
able to met only the Alice(s) having the correlated spin.


​Why?


Very good question!

Bruce

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 10/06/2017 2:36 am, Telmo Menezes wrote:

On Fri, Jun 9, 2017 at 12:37 AM, Bruce Kellett


The idea that the explanation is epistemological rather that ontological has
been my preferred position for a long time. If the wave-function is merely
an epistemological device for calculating probabilities and not a really
existing object, all worries about collapse and action-at-a-distance vanish.
Of course, multi worlds also vanish, but in my opinion that is no bad thing.

So what's your position on Deutsch's argument about quantum computers?
Where does the extra computing power come from?


It has long been understood that Deutsch is out to lunch on this. He 
appears to assume that a quantum computer is just using the same 
algorithms that a classical computer would use, only executing them in a 
massively parallel manner. This is manifestly false. Quantum computers 
operate in a completely different way -- that is why there are so few 
actual algorithms for quantum computers to execute that gain massive 
speed improvements.


As Brent says in his recent post, Scott Aaronson points out:
"The way a quantum algorithms work is that they arrange for wrong 
answers to destructively interfere while the desired answer interferes 
constructively. Interference requires that they take place in the same 
world."


Classical computers do not have quantum interference. Quantum computing 
does not prove the existence of parallel worlds -- there is no need for 
other worlds in which to find the computational power, you just need a 
modicum of insight into how quantum computing algorithms work.


You might claim that Deutsch is a known expert on quantum computing, but 
more commonly, Deutsch is known for having way out, non-standard ideas 
on quantum mechanics.


Bruce

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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 9 June 2017 at 12:34, Bruno Marchal  wrote:

>
> On 08 Jun 2017, at 02:05, Bruce Kellett wrote:
>
> On 7/06/2017 10:38 pm, Bruno Marchal wrote:
>>
>>> On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
>>> On 7/06/2017 7:09 pm, Bruno Marchal wrote:
>>>
 On 06 Jun 2017, at 01:23, Bruce Kellett wrote:
>
> I have been through this before. I looked at Price again this morning
>> and was frankly appalled at the stupidity of what I saw.
>> Let me summarize briefly what he did. He has a very cumbersome
>> notation, but I will attempt to simplify as far as is possible. I will 
>> use
>> '+' and '-' as spin states, rather than his 'left', 'right'.
>>
>> He write the initial wave function as for the case when you and I
>> agree in advance to have aligned polarizers:
>>
>> |psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
>>   = |me, +,-,you> - |me,-,+,you>
>>
>> He says that at this point no measurements have been made, and
>> neither observer is split. But his fundamental mistake is already 
>> present.
>>
>> A little test for you: what is wrong with the above set of equations
>> from a no-collapse pov?
>>
>> skipping some tedium, he then gets
>>
>> |psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>
>>
>> where the notation me[+] etc means I have measured '+', you[-] means
>> you have measured '-'.
>>
>> He then claims that the QM results of perfect anticorrelation in the
>> case of parallel polarizers has been recovered without any non-local
>> interaction!
>>
>> Spoiler -- in order to write the final line for |psi_1> he has
>> already assumed collapse, when I measure '+', you are presented *only* 
>> with
>> '-', so of course you get the right result -- he has built that
>> non-locality in from the start.
>>
>
> ?
>
> From the start shows that it is local.
>

 Your failure to see the problem here is symptomatic of your complete
 failure to understand EPR in the MWI.

>>>
>>> I could say the same, but emphatic statements are not helping. My
>>> feeling is that you interpret the singlet state above like if it prepares
>>> Alice and Bob particles in the respective + and - states, but that is not
>>> the case. The singlet state describe a multiverse where Alice and Bob have
>>> all possible states, yet correlated.
>>>
>>
>> The singlet state is rotationally invariant, yes, and can be expanded in
>> any basis of the 2-d complex Hilbert space. That has never been in doubt.
>>
>
> OK.
>
>
>
>> Then in absence of collapse, all interactions, and results are obtained
>>> locally, and does not need to be correlated until they spread at low speed
>>> up their partners.
>>>
>>
>> That does not follow. Although there are an infinity of possible bases
>> for the singlet state, these are potential only,
>>
>
> I don't understand this. Potential? That is no more the MW.
>
>
>
>
>
> and do not exist in any operative sense until the state interacts with
>> something that sets a direction.
>>
>
> That looks more like Bohr than Everett.
>
>
>
>
> You appear to claim that A and B exist in separate worlds corresponding to
>> each of this infinity of bases.
>>
>
> Yes. It is the rotaional invariance of the singlet states "taken
> seriously" when we drop the idea of collapse, or of special dualism between
> observer and the observed.
>
>
>
>
> But that is a misunderstanding. They are in superpositions in every base,
>> sure, but that does not mean that there are 'worlds' corresponding to each
>> possible base until some external interaction occurs.
>>
>
> This is even more fuzzy than the collapse. It looks like consciousness not
> only reduce the wave, but create the physical reality. That is correct in
> Mechanism, but that is another story.
>
>
>
> As you yourself have said, a world is something that is closed to
>> interaction. But superpositions are not closed to interaction, they can
>> interfere -- as in the two slit experiment, and essentially every other
>> application of QM.
>>
>
> Right.
>
>
>
>> So there are no separate worlds corresponding to every possible
>> orientation of the polarizers. Worlds can arise only after interaction and
>> decoherence has progressed so that the overlap between the branches of the
>> superposition is zero (FAPP if you like). It is only then that the branches
>> can no longer interfere (interact) and are closed to interaction, and thus
>> constitute different worlds.
>>
>
> We will have to disagree with this. I use the Y=II rules, like Deutsch. In
> this case the reading of the singlet state gives 2^aleph_zero constantly
> spreading histories figuring Bob and Alice. With mechanism, those
> worlds/histories are more like dreams. They will be epistemological
> personal (and plural in the spreading interaction based spheres).
>
>
>
>
>> The standard procedure in quantum mechanics when one is faced wit

Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

On Fri, Jun 9, 2017 at 12:37 AM, Bruce Kellett
 wrote:
> On 8/06/2017 11:25 pm, David Nyman wrote:
>
> On 8 Jun 2017 12:50 p.m., "Bruce Kellett"  wrote:
>
> On 8/06/2017 9:06 pm, David Nyman wrote:
>
>
> Yes, this is also the point where I stumble. I've been trying somewhat
> inarticulately to characterise a possibly non-miraculous approach from a
> slightly different perspective. Suppose we think about the matter from the
> point of view of Hoyle's pigeonholes. Perhaps there are pigeonholes that in
> some sense correspond to observations that are 'malformed' with respect to
> the predictions of QM. Now, we are presumably to suppose that the
> entanglement which leads to well-formed predictions embodies a very
> fundamental aspect of physical reality and consequently also the possibility
> of meaningful observation. Hence any such malformed 'observations' should by
> the same assumption be considered of very low measure, in the sense of any
> possible contribution to Hoyle's conceptualised sum of well-formed
> observation.
>
> I suppose what I'm suggesting is that something fundamental and highly
> constraining about the demands of observation of a consistent physical
> environment itself effectively filters out what is possible but incompatible
> with those demands. Is this irretrievably circular?
>
>
> I don't think it is so much circular as conspiratorial. If physical results
> were to come about in such a conspiratorial way, rather than
> straightforwardly from the formalism as in quantum non-locality, one might
> wonder what the scientific enterprise is really all about. (Rather as
> Zeilinger wondered about superdeterminism.)
>
>
> I'm not sure I agree that it would be conspiratorial. Non-locality as a
> consequence of entanglement would be central to the explanation in that it
> would fix the very limits of what it would be possible to observe for a
> deeply physical reason. I'm also not entirely convinced that the idea would
> necessarily be at odds with the scientific enterprise per se. That would be
> a question of the restrictions one wished to place on its explanatory
> approach. Much the same has been remarked about cosmological Multiverse
> theories, or the String Landscape, but ISTM that those judgements - whether
> they turn out to be right or wrong -  are based on little more than a
> long-standing presupposition that there must be a unique solution to certain
> equations.
>
> However I concede that whereas what I've outlined isn't necessarily
> inconsistent with the predictions of the quantum formalism (else it would
> just be wrong) it would depend on a presently rather non-standard notion of
> 'unobservable'. That notion would in turn require us to understand the
> formalism, at a very fundamental level, as describing an emergent
> epistemological phenomenon rather than a basic ontological one. To that
> degree it may be more compatible with an explanatory schema such as
> computationalism, in terms of which physics is indeed an epistemological
> emergent, as distinct from physics tout simple.
>
>
> The idea that the explanation is epistemological rather that ontological has
> been my preferred position for a long time. If the wave-function is merely
> an epistemological device for calculating probabilities and not a really
> existing object, all worries about collapse and action-at-a-distance vanish.
> Of course, multi worlds also vanish, but in my opinion that is no bad thing.

So what's your position on Deutsch's argument about quantum computers?
Where does the extra computing power come from?

Telmo.

> Bruce
>
>
>
>
>
>
> --
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> "Everything List" group.
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> email to everything-list+unsubscr...@googlegroups.com.
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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 08 Jun 2017, at 02:05, Bruce Kellett wrote:


On 7/06/2017 10:38 pm, Bruno Marchal wrote:

On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
On 7/06/2017 7:09 pm, Bruno Marchal wrote:

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome  
notation, but I will attempt to simplify as far as is possible.  
I will use '+' and '-' as spin states, rather than his 'left',  
'right'.


He write the initial wave function as for the case when you and  
I agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
  = |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and  
neither observer is split. But his fundamental mistake is  
already present.


A little test for you: what is wrong with the above set of  
equations from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-]  
means you have measured '-'.


He then claims that the QM results of perfect anticorrelation in  
the case of parallel polarizers has been recovered without any  
non-local interaction!


Spoiler -- in order to write the final line for |psi_1> he has  
already assumed collapse, when I measure '+', you are presented  
*only* with '-', so of course you get the right result -- he has  
built that non-locality in from the start.


?

From the start shows that it is local.


Your failure to see the problem here is symptomatic of your  
complete failure to understand EPR in the MWI.


I could say the same, but emphatic statements are not helping. My  
feeling is that you interpret the singlet state above like if it  
prepares Alice and Bob particles in the respective + and - states,  
but that is not the case. The singlet state describe a multiverse  
where Alice and Bob have all possible states, yet correlated.


The singlet state is rotationally invariant, yes, and can be  
expanded in any basis of the 2-d complex Hilbert space. That has  
never been in doubt.


OK.




Then in absence of collapse, all interactions, and results are  
obtained locally, and does not need to be correlated until they  
spread at low speed up their partners.


That does not follow. Although there are an infinity of possible  
bases for the singlet state, these are potential only,


I don't understand this. Potential? That is no more the MW.





and do not exist in any operative sense until the state interacts  
with something that sets a direction.


That looks more like Bohr than Everett.




You appear to claim that A and B exist in separate worlds  
corresponding to each of this infinity of bases.


Yes. It is the rotaional invariance of the singlet states "taken  
seriously" when we drop the idea of collapse, or of special dualism  
between observer and the observed.





But that is a misunderstanding. They are in superpositions in every  
base, sure, but that does not mean that there are 'worlds'  
corresponding to each possible base until some external interaction  
occurs.


This is even more fuzzy than the collapse. It looks like consciousness  
not only reduce the wave, but create the physical reality. That is  
correct in Mechanism, but that is another story.




As you yourself have said, a world is something that is closed to  
interaction. But superpositions are not closed to interaction, they  
can interfere -- as in the two slit experiment, and essentially  
every other application of QM.


Right.




So there are no separate worlds corresponding to every possible  
orientation of the polarizers. Worlds can arise only after  
interaction and decoherence has progressed so that the overlap  
between the branches of the superposition is zero (FAPP if you  
like). It is only then that the branches can no longer interfere  
(interact) and are closed to interaction, and thus constitute  
different worlds.


We will have to disagree with this. I use the Y=II rules, like  
Deutsch. In this case the reading of the singlet state gives  
2^aleph_zero constantly spreading histories figuring Bob and Alice.  
With mechanism, those worlds/histories are more like dreams. They will  
be epistemological personal (and plural in the spreading interaction  
based spheres).






The standard procedure in quantum mechanics when one is faced with a  
superposition that interacts with something external, is to expand  
the superposition in a base that corresponds to the external context.


OK. In this case, Alice choose to measure her spin. This will only  
self-localized here in one (actually still aleph_0) histories, where  
she will know her states, and the states of any Bob she could soon or  
later interact with, but not of the inaccessible Bobs, who might found  
non correlated r

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 8/06/2017 11:25 pm, David Nyman wrote:
On 8 Jun 2017 12:50 p.m., "Bruce Kellett" > wrote:


On 8/06/2017 9:06 pm, David Nyman wrote:


Yes, this is also the point where I stumble. I've been trying
somewhat inarticulately to characterise a possibly non-miraculous
approach from a slightly different perspective. Suppose we think
about the matter from the point of view of Hoyle's pigeonholes.
Perhaps there are pigeonholes that in some sense correspond to
observations that are 'malformed' with respect to the predictions
of QM. Now, we are presumably to suppose that the entanglement
which leads to well-formed predictions embodies a very
fundamental aspect of physical reality and consequently also the
possibility of meaningful observation. Hence any such malformed
'observations' should by the same assumption be considered of
very low measure, in the sense of any possible contribution to
Hoyle's conceptualised sum of well-formed observation.

I suppose what I'm suggesting is that something fundamental and
highly constraining about the demands of observation of a
consistent physical environment itself effectively filters out
what is possible but incompatible with those demands. Is this
irretrievably circular?


I don't think it is so much circular as conspiratorial. If
physical results were to come about in such a conspiratorial way,
rather than straightforwardly from the formalism as in quantum
non-locality, one might wonder what the scientific enterprise is
really all about. (Rather as Zeilinger wondered about
superdeterminism.)


I'm not sure I agree that it would be conspiratorial. Non-locality as 
a consequence of entanglement would be central to the explanation in 
that it would fix the very limits of what it would be possible to 
observe for a deeply physical reason. I'm also not entirely convinced 
that the idea would necessarily be at odds with the scientific 
enterprise per se. That would be a question of the restrictions one 
wished to place on its explanatory approach. Much the same has been 
remarked about cosmological Multiverse theories, or the String 
Landscape, but ISTM that those judgements - whether they turn out to 
be right or wrong -  are based on little more than a long-standing 
presupposition that there must be a unique solution to certain equations.


However I concede that whereas what I've outlined isn't necessarily 
inconsistent with the predictions of the quantum formalism (else it 
would just be wrong) it would depend on a presently rather 
non-standard notion of 'unobservable'. That notion would in turn 
require us to understand the formalism, at a very fundamental level, 
as describing an emergent epistemological phenomenon rather than a 
basic ontological one. To that degree it may be more compatible with 
an explanatory schema such as computationalism, in terms of which 
physics is indeed an epistemological emergent, as distinct from 
physics tout simple.


The idea that the explanation is epistemological rather that ontological 
has been my preferred position for a long time. If the wave-function is 
merely an epistemological device for calculating probabilities and not a 
really existing object, all worries about collapse and 
action-at-a-distance vanish. Of course, multi worlds also vanish, but in 
my opinion that is no bad thing.


Bruce






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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 8 Jun 2017 12:50 p.m., "Bruce Kellett"  wrote:

On 8/06/2017 9:06 pm, David Nyman wrote:

On 8 Jun 2017 11:40 a.m., "Bruce Kellett"  wrote:

On 8/06/2017 7:52 pm, David Nyman wrote:

On 8 Jun 2017 1:05 a.m., "Bruce Kellett" < 
bhkell...@optusnet.com.au> wrote:


The question then, is whether many worlds can provide a fully local account
of this situation. I claim, with most present day physicists, that MWI does
not provide any such local account.


I suspect I'm being obtuse in some way here but, rereading the quote
attributed to Bell himself by Wikipedia about superdeterminism, it strikes
me that MWI seems to describe a species of this sort of thing. IOW when
Alice and Bob make their measurements, the consequence in terms of branches
is a spectrum of all the possible outcomes. Indeed one could say that this
is what has been propagating from one to the other, rather than a
'particle'. Let's say then that the various versions of Alice and Bob that
consequently coexist in MWI terms, however far apart they may have been,
eventually meet to compare notes. Again, the spectrum of possible outcomes
implicit in the global MWI perspective travels with them, as it were.
However, of all the possible pairings of the two, it appears to be
'superdetermined' that each observed encounter must be consistent with the
predictions of QM. And so it would appear that the paired results of their
joint measurements are somehow inseparable, in Wallace's language, without
there having been any action at a distance. If this depiction were to make
any sense, one might then enquire what common cause, or other explanatory
device, could account for this apparent superdetermination of observed
outcomes?


I don't think that superdeterminism and MWI have very much in common.
Although Bell did acknowledge that superdeterminism provides a possible
local loophole to his theorem, Bell always thought that superdeterminism
was sufficiently implausible to be disregarded as a serious contender as an
explanation.

I tend to agree with the comment from Zeilinger on the same Wiki page, to
the effect that such absolute superdeterminism would render the whole
scientific enterprise otiose. I think that non-locality is a better
approach -- at least then  science can still make sense.

The problem with attempts to find local accounts of the correlations
between Alice and Bob is that their measurements are taken to be
independent. If they are independent, then they cannot be correlated --
that is in the definition of independence. Superdeterminism circumvents
this, simply by denying that Alice and Bob can freely choose their
measurements, and are consequently not independent.

As I understand the better attempts to give an account in MWI, it is
accepted that Alice and Bob are independent, so their results are
uncorrelated *when they are made*, but the necessary correlation is built
later when they meet to compare results. I find this unconvincing, and no
satisfactory account of any mechanism whereby this could be achieved has
been given. Accounts along this line seem to depend on multiple worlds
containing all possible results that somehow, miraculously, pair up,
without any outside intervention, in such a way to give the necessary
correlations. This is rendered less plausible if one considers timelike
separations, where Bob, say, is always in Alice's forward light cone, so
any splitting of either observer is communicated to the other by normal
decoherence, long before the other measurement is made, and before they
meet up to compare lab books.


Yes, this is also the point where I stumble. I've been trying somewhat
inarticulately to characterise a possibly non-miraculous approach from a
slightly different perspective. Suppose we think about the matter from the
point of view of Hoyle's pigeonholes. Perhaps there are pigeonholes that in
some sense correspond to observations that are 'malformed' with respect to
the predictions of QM. Now, we are presumably to suppose that the
entanglement which leads to well-formed predictions embodies a very
fundamental aspect of physical reality and consequently also the
possibility of meaningful observation. Hence any such malformed
'observations' should by the same assumption be considered of very low
measure, in the sense of any possible contribution to Hoyle's
conceptualised sum of well-formed observation.

I suppose what I'm suggesting is that something fundamental and highly
constraining about the demands of observation of a consistent physical
environment itself effectively filters out what is possible but
incompatible with those demands. Is this irretrievably circular?


I don't think it is so much circular as conspiratorial. If physical results
were to come about in such a conspiratorial way, rather than
straightforwardly from the formalism as in quantum non-locality, one might
wonder what the scientific enterprise is really all about. (Rather as
Zeilinger wondered about superdeterminism.)


I'm not sure I agr

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 8/06/2017 9:06 pm, David Nyman wrote:
On 8 Jun 2017 11:40 a.m., "Bruce Kellett" > wrote:


On 8/06/2017 7:52 pm, David Nyman wrote:

On 8 Jun 2017 1:05 a.m., "Bruce Kellett"
mailto:bhkell...@optusnet.com.au>> wrote:


The question then, is whether many worlds can provide a fully
local account of this situation. I claim, with most present
day physicists, that MWI does not provide any such local account.


I suspect I'm being obtuse in some way here but, rereading the
quote attributed to Bell himself by Wikipedia about
superdeterminism, it strikes me that MWI seems to describe a
species of this sort of thing. IOW when Alice and Bob make their
measurements, the consequence in terms of branches is a spectrum
of all the possible outcomes. Indeed one could say that this is
what has been propagating from one to the other, rather than a
'particle'. Let's say then that the various versions of Alice and
Bob that consequently coexist in MWI terms, however far apart
they may have been, eventually meet to compare notes. Again, the
spectrum of possible outcomes implicit in the global MWI
perspective travels with them, as it were. However, of all the
possible pairings of the two, it appears to be 'superdetermined'
that each observed encounter must be consistent with the
predictions of QM. And so it would appear that the paired results
of their joint measurements are somehow inseparable, in Wallace's
language, without there having been any action at a distance. If
this depiction were to make any sense, one might then enquire
what common cause, or other explanatory device, could account for
this apparent superdetermination of observed outcomes?


I don't think that superdeterminism and MWI have very much in
common. Although Bell did acknowledge that superdeterminism
provides a possible local loophole to his theorem, Bell always
thought that superdeterminism was sufficiently implausible to be
disregarded as a serious contender as an explanation.

I tend to agree with the comment from Zeilinger on the same Wiki
page, to the effect that such absolute superdeterminism would
render the whole scientific enterprise otiose. I think that
non-locality is a better approach -- at least then  science can
still make sense.

The problem with attempts to find local accounts of the
correlations between Alice and Bob is that their measurements are
taken to be independent. If they are independent, then they cannot
be correlated -- that is in the definition of independence.
Superdeterminism circumvents this, simply by denying that Alice
and Bob can freely choose their measurements, and are consequently
not independent.

As I understand the better attempts to give an account in MWI, it
is accepted that Alice and Bob are independent, so their results
are uncorrelated *when they are made*, but the necessary
correlation is built later when they meet to compare results. I
find this unconvincing, and no satisfactory account of any
mechanism whereby this could be achieved has been given. Accounts
along this line seem to depend on multiple worlds containing all
possible results that somehow, miraculously, pair up, without any
outside intervention, in such a way to give the necessary
correlations. This is rendered less plausible if one considers
timelike separations, where Bob, say, is always in Alice's forward
light cone, so any splitting of either observer is communicated to
the other by normal decoherence, long before the other measurement
is made, and before they meet up to compare lab books.


Yes, this is also the point where I stumble. I've been trying somewhat 
inarticulately to characterise a possibly non-miraculous approach from 
a slightly different perspective. Suppose we think about the matter 
from the point of view of Hoyle's pigeonholes. Perhaps there are 
pigeonholes that in some sense correspond to observations that are 
'malformed' with respect to the predictions of QM. Now, we are 
presumably to suppose that the entanglement which leads to well-formed 
predictions embodies a very fundamental aspect of physical reality and 
consequently also the possibility of meaningful observation. Hence any 
such malformed 'observations' should by the same assumption be 
considered of very low measure, in the sense of any possible 
contribution to Hoyle's conceptualised sum of well-formed observation.


I suppose what I'm suggesting is that something fundamental and highly 
constraining about the demands of observation of a consistent physical 
environment itself effectively filters out what is possible but 
incompatible with those demands. Is this irretrievably circular?


I don't think it is so much circular as conspiratorial. If physical 
results were to come about in su

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 8 Jun 2017 11:40 a.m., "Bruce Kellett"  wrote:

On 8/06/2017 7:52 pm, David Nyman wrote:

On 8 Jun 2017 1:05 a.m., "Bruce Kellett" < 
bhkell...@optusnet.com.au> wrote:


The question then, is whether many worlds can provide a fully local account
of this situation. I claim, with most present day physicists, that MWI does
not provide any such local account.


I suspect I'm being obtuse in some way here but, rereading the quote
attributed to Bell himself by Wikipedia about superdeterminism, it strikes
me that MWI seems to describe a species of this sort of thing. IOW when
Alice and Bob make their measurements, the consequence in terms of branches
is a spectrum of all the possible outcomes. Indeed one could say that this
is what has been propagating from one to the other, rather than a
'particle'. Let's say then that the various versions of Alice and Bob that
consequently coexist in MWI terms, however far apart they may have been,
eventually meet to compare notes. Again, the spectrum of possible outcomes
implicit in the global MWI perspective travels with them, as it were.
However, of all the possible pairings of the two, it appears to be
'superdetermined' that each observed encounter must be consistent with the
predictions of QM. And so it would appear that the paired results of their
joint measurements are somehow inseparable, in Wallace's language, without
there having been any action at a distance. If this depiction were to make
any sense, one might then enquire what common cause, or other explanatory
device, could account for this apparent superdetermination of observed
outcomes?


I don't think that superdeterminism and MWI have very much in common.
Although Bell did acknowledge that superdeterminism provides a possible
local loophole to his theorem, Bell always thought that superdeterminism
was sufficiently implausible to be disregarded as a serious contender as an
explanation.

I tend to agree with the comment from Zeilinger on the same Wiki page, to
the effect that such absolute superdeterminism would render the whole
scientific enterprise otiose. I think that non-locality is a better
approach -- at least then  science can still make sense.

The problem with attempts to find local accounts of the correlations
between Alice and Bob is that their measurements are taken to be
independent. If they are independent, then they cannot be correlated --
that is in the definition of independence. Superdeterminism circumvents
this, simply by denying that Alice and Bob can freely choose their
measurements, and are consequently not independent.

As I understand the better attempts to give an account in MWI, it is
accepted that Alice and Bob are independent, so their results are
uncorrelated *when they are made*, but the necessary correlation is built
later when they meet to compare results. I find this unconvincing, and no
satisfactory account of any mechanism whereby this could be achieved has
been given. Accounts along this line seem to depend on multiple worlds
containing all possible results that somehow, miraculously, pair up,
without any outside intervention, in such a way to give the necessary
correlations. This is rendered less plausible if one considers timelike
separations, where Bob, say, is always in Alice's forward light cone, so
any splitting of either observer is communicated to the other by normal
decoherence, long before the other measurement is made, and before they
meet up to compare lab books.


Yes, this is also the point where I stumble. I've been trying somewhat
inarticulately to characterise a possibly non-miraculous approach from a
slightly different perspective. Suppose we think about the matter from the
point of view of Hoyle's pigeonholes. Perhaps there are pigeonholes that in
some sense correspond to observations that are 'malformed' with respect to
the predictions of QM. Now, we are presumably to suppose that the
entanglement which leads to well-formed predictions embodies a very
fundamental aspect of physical reality and consequently also the
possibility of meaningful observation. Hence any such malformed
'observations' should by the same assumption be considered of very low
measure, in the sense of any possible contribution to Hoyle's
conceptualised sum of well-formed observation.

I suppose what I'm suggesting is that something fundamental and highly
constraining about the demands of observation of a consistent physical
environment itself effectively filters out what is possible but
incompatible with those demands. Is this irretrievably circular?

David



Bruce

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Re: A thought on MWI and its alternative(s)

[Quentin Anciaux]

http://mccabism.blogspot.be/2010/10/many-worlds-and-quantum-fungibility.html


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2017-06-08 12:57 GMT+02:00 Quentin Anciaux :

>
>
> 2017-06-08 12:40 GMT+02:00 Bruce Kellett :
>
>> On 8/06/2017 7:52 pm, David Nyman wrote:
>>
>> On 8 Jun 2017 1:05 a.m., "Bruce Kellett" < 
>> bhkell...@optusnet.com.au> wrote:
>>
>>
>> The question then, is whether many worlds can provide a fully local
>> account of this situation. I claim, with most present day physicists, that
>> MWI does not provide any such local account.
>>
>>
>> I suspect I'm being obtuse in some way here but, rereading the quote
>> attributed to Bell himself by Wikipedia about superdeterminism, it strikes
>> me that MWI seems to describe a species of this sort of thing. IOW when
>> Alice and Bob make their measurements, the consequence in terms of branches
>> is a spectrum of all the possible outcomes. Indeed one could say that this
>> is what has been propagating from one to the other, rather than a
>> 'particle'. Let's say then that the various versions of Alice and Bob that
>> consequently coexist in MWI terms, however far apart they may have been,
>> eventually meet to compare notes. Again, the spectrum of possible outcomes
>> implicit in the global MWI perspective travels with them, as it were.
>> However, of all the possible pairings of the two, it appears to be
>> 'superdetermined' that each observed encounter must be consistent with the
>> predictions of QM. And so it would appear that the paired results of their
>> joint measurements are somehow inseparable, in Wallace's language, without
>> there having been any action at a distance. If this depiction were to make
>> any sense, one might then enquire what common cause, or other explanatory
>> device, could account for this apparent superdetermination of observed
>> outcomes?
>>
>>
>> I don't think that superdeterminism and MWI have very much in common.
>> Although Bell did acknowledge that superdeterminism provides a possible
>> local loophole to his theorem, Bell always thought that superdeterminism
>> was sufficiently implausible to be disregarded as a serious contender as an
>> explanation.
>>
>> I tend to agree with the comment from Zeilinger on the same Wiki page, to
>> the effect that such absolute superdeterminism would render the whole
>> scientific enterprise otiose. I think that non-locality is a better
>> approach -- at least then  science can still make sense.
>>
>> The problem with attempts to find local accounts of the correlations
>> between Alice and Bob is that their measurements are taken to be
>> independent. If they are independent, then they cannot be correlated --
>> that is in the definition of independence. Superdeterminism circumvents
>> this, simply by denying that Alice and Bob can freely choose their
>> measurements, and are consequently not independent.
>>
>> As I understand the better attempts to give an account in MWI, it is
>> accepted that Alice and Bob are independent, so their results are
>> uncorrelated *when they are made*, but the necessary correlation is built
>> later when they meet to compare results. I find this unconvincing, and no
>> satisfactory account of any mechanism whereby this could be achieved has
>> been given. Accounts along this line seem to depend on multiple worlds
>> containing all possible results that somehow, miraculously, pair up,
>> without any outside intervention, in such a way to give the necessary
>> correlations. This is rendered less plausible if one considers timelike
>> separations, where Bob, say, is always in Alice's forward light cone, so
>> any splitting of either observer is communicated to the other by normal
>> decoherence, long before the other measurement is made, and before they
>> meet up to compare lab books.
>>
>>
> If I remember David Deutsch explained that the worlds were not "splitting"
> but differentiating, and thus are all preexisting... so even if their
> measures are independent, this gives only a self localisation... and so
> nothing non-local happens ?
>
> Quentin
>
>
>
>
>
>> Bruce
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "Everything List" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to everything-list+unsubscr...@googlegroups.com.
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>>
>
>
>
> --
> All those moments will be lost in time, like tears in rain. (Roy
> Batty/Rutger Hauer)
>
>
> 

Re: A thought on MWI and its alternative(s)

[Quentin Anciaux]

2017-06-08 12:40 GMT+02:00 Bruce Kellett :

> On 8/06/2017 7:52 pm, David Nyman wrote:
>
> On 8 Jun 2017 1:05 a.m., "Bruce Kellett" < 
> bhkell...@optusnet.com.au> wrote:
>
>
> The question then, is whether many worlds can provide a fully local
> account of this situation. I claim, with most present day physicists, that
> MWI does not provide any such local account.
>
>
> I suspect I'm being obtuse in some way here but, rereading the quote
> attributed to Bell himself by Wikipedia about superdeterminism, it strikes
> me that MWI seems to describe a species of this sort of thing. IOW when
> Alice and Bob make their measurements, the consequence in terms of branches
> is a spectrum of all the possible outcomes. Indeed one could say that this
> is what has been propagating from one to the other, rather than a
> 'particle'. Let's say then that the various versions of Alice and Bob that
> consequently coexist in MWI terms, however far apart they may have been,
> eventually meet to compare notes. Again, the spectrum of possible outcomes
> implicit in the global MWI perspective travels with them, as it were.
> However, of all the possible pairings of the two, it appears to be
> 'superdetermined' that each observed encounter must be consistent with the
> predictions of QM. And so it would appear that the paired results of their
> joint measurements are somehow inseparable, in Wallace's language, without
> there having been any action at a distance. If this depiction were to make
> any sense, one might then enquire what common cause, or other explanatory
> device, could account for this apparent superdetermination of observed
> outcomes?
>
>
> I don't think that superdeterminism and MWI have very much in common.
> Although Bell did acknowledge that superdeterminism provides a possible
> local loophole to his theorem, Bell always thought that superdeterminism
> was sufficiently implausible to be disregarded as a serious contender as an
> explanation.
>
> I tend to agree with the comment from Zeilinger on the same Wiki page, to
> the effect that such absolute superdeterminism would render the whole
> scientific enterprise otiose. I think that non-locality is a better
> approach -- at least then  science can still make sense.
>
> The problem with attempts to find local accounts of the correlations
> between Alice and Bob is that their measurements are taken to be
> independent. If they are independent, then they cannot be correlated --
> that is in the definition of independence. Superdeterminism circumvents
> this, simply by denying that Alice and Bob can freely choose their
> measurements, and are consequently not independent.
>
> As I understand the better attempts to give an account in MWI, it is
> accepted that Alice and Bob are independent, so their results are
> uncorrelated *when they are made*, but the necessary correlation is built
> later when they meet to compare results. I find this unconvincing, and no
> satisfactory account of any mechanism whereby this could be achieved has
> been given. Accounts along this line seem to depend on multiple worlds
> containing all possible results that somehow, miraculously, pair up,
> without any outside intervention, in such a way to give the necessary
> correlations. This is rendered less plausible if one considers timelike
> separations, where Bob, say, is always in Alice's forward light cone, so
> any splitting of either observer is communicated to the other by normal
> decoherence, long before the other measurement is made, and before they
> meet up to compare lab books.
>
>
If I remember David Deutsch explained that the worlds were not "splitting"
but differentiating, and thus are all preexisting... so even if their
measures are independent, this gives only a self localisation... and so
nothing non-local happens ?

Quentin





> Bruce
>
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>



-- 
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Batty/Rutger Hauer)


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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 8/06/2017 7:52 pm, David Nyman wrote:
On 8 Jun 2017 1:05 a.m., "Bruce Kellett" > wrote:



The question then, is whether many worlds can provide a fully
local account of this situation. I claim, with most present day
physicists, that MWI does not provide any such local account.


I suspect I'm being obtuse in some way here but, rereading the quote 
attributed to Bell himself by Wikipedia about superdeterminism, it 
strikes me that MWI seems to describe a species of this sort of thing. 
IOW when Alice and Bob make their measurements, the consequence in 
terms of branches is a spectrum of all the possible outcomes. Indeed 
one could say that this is what has been propagating from one to the 
other, rather than a 'particle'. Let's say then that the various 
versions of Alice and Bob that consequently coexist in MWI terms, 
however far apart they may have been, eventually meet to compare 
notes. Again, the spectrum of possible outcomes implicit in the global 
MWI perspective travels with them, as it were. However, of all the 
possible pairings of the two, it appears to be 'superdetermined' that 
each observed encounter must be consistent with the predictions of QM. 
And so it would appear that the paired results of their joint 
measurements are somehow inseparable, in Wallace's language, without 
there having been any action at a distance. If this depiction were to 
make any sense, one might then enquire what common cause, or other 
explanatory device, could account for this apparent superdetermination 
of observed outcomes?


I don't think that superdeterminism and MWI have very much in common. 
Although Bell did acknowledge that superdeterminism provides a possible 
local loophole to his theorem, Bell always thought that superdeterminism 
was sufficiently implausible to be disregarded as a serious contender as 
an explanation.


I tend to agree with the comment from Zeilinger on the same Wiki page, 
to the effect that such absolute superdeterminism would render the whole 
scientific enterprise otiose. I think that non-locality is a better 
approach -- at least then  science can still make sense.


The problem with attempts to find local accounts of the correlations 
between Alice and Bob is that their measurements are taken to be 
independent. If they are independent, then they cannot be correlated -- 
that is in the definition of independence. Superdeterminism circumvents 
this, simply by denying that Alice and Bob can freely choose their 
measurements, and are consequently not independent.


As I understand the better attempts to give an account in MWI, it is 
accepted that Alice and Bob are independent, so their results are 
uncorrelated *when they are made*, but the necessary correlation is 
built later when they meet to compare results. I find this unconvincing, 
and no satisfactory account of any mechanism whereby this could be 
achieved has been given. Accounts along this line seem to depend on 
multiple worlds containing all possible results that somehow, 
miraculously, pair up, without any outside intervention, in such a way 
to give the necessary correlations. This is rendered less plausible if 
one considers timelike separations, where Bob, say, is always in Alice's 
forward light cone, so any splitting of either observer is communicated 
to the other by normal decoherence, long before the other measurement is 
made, and before they meet up to compare lab books.


Bruce

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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 8 Jun 2017 1:05 a.m., "Bruce Kellett"  wrote:

On 7/06/2017 10:38 pm, Bruno Marchal wrote:

> On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
> On 7/06/2017 7:09 pm, Bruno Marchal wrote:
>
>> On 06 Jun 2017, at 01:23, Bruce Kellett wrote:
>>>
>>> I have been through this before. I looked at Price again this morning
 and was frankly appalled at the stupidity of what I saw.
 Let me summarize briefly what he did. He has a very cumbersome
 notation, but I will attempt to simplify as far as is possible. I will use
 '+' and '-' as spin states, rather than his 'left', 'right'.

 He write the initial wave function as for the case when you and I agree
 in advance to have aligned polarizers:

 |psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
= |me, +,-,you> - |me,-,+,you>

 He says that at this point no measurements have been made, and neither
 observer is split. But his fundamental mistake is already present.

 A little test for you: what is wrong with the above set of equations
 from a no-collapse pov?

 skipping some tedium, he then gets

 |psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

 where the notation me[+] etc means I have measured '+', you[-] means
 you have measured '-'.

 He then claims that the QM results of perfect anticorrelation in the
 case of parallel polarizers has been recovered without any non-local
 interaction!

 Spoiler -- in order to write the final line for |psi_1> he has already
 assumed collapse, when I measure '+', you are presented *only* with '-', so
 of course you get the right result -- he has built that non-locality in
 from the start.

>>>
>>> ?
>>>
>>> From the start shows that it is local.
>>>
>>
>> Your failure to see the problem here is symptomatic of your complete
>> failure to understand EPR in the MWI.
>>
>
> I could say the same, but emphatic statements are not helping. My feeling
> is that you interpret the singlet state above like if it prepares Alice and
> Bob particles in the respective + and - states, but that is not the case.
> The singlet state describe a multiverse where Alice and Bob have all
> possible states, yet correlated.
>

The singlet state is rotationally invariant, yes, and can be expanded in
any basis of the 2-d complex Hilbert space. That has never been in doubt.


Then in absence of collapse, all interactions, and results are obtained
> locally, and does not need to be correlated until they spread at low speed
> up their partners.
>

That does not follow. Although there are an infinity of possible bases for
the singlet state, these are potential only, and do not exist in any
operative sense until the state interacts with something that sets a
direction. You appear to claim that A and B exist in separate worlds
corresponding to each of this infinity of bases. But that is a
misunderstanding. They are in superpositions in every base, sure, but that
does not mean that there are 'worlds' corresponding to each possible base
until some external interaction occurs. As you yourself have said, a world
is something that is closed to interaction. But superpositions are not
closed to interaction, they can interfere -- as in the two slit experiment,
and essentially every other application of QM.

So there are no separate worlds corresponding to every possible orientation
of the polarizers. Worlds can arise only after interaction and decoherence
has progressed so that the overlap between the branches of the
superposition is zero (FAPP if you like). It is only then that the branches
can no longer interfere (interact) and are closed to interaction, and thus
constitute different worlds.

The standard procedure in quantum mechanics when one is faced with a
superposition that interacts with something external, is to expand the
superposition in a base that corresponds to the external context. That is
what happens when an unpolarized spin meets a polarizer aligned in a
particular direction -- one expands the rotationally symmetric unpolarized
state in the basis matching the external context. That is all that is
happening with the singlet state above; when Alice comes to measure the
symmetric state, it is convenient to expand the singlet state in a basis
that corresponds to the orientation of Alice's polarizer. Then the result
of the interaction is easily calculated. If one use some other basis, in
some other direction, one would end up with a superposition of states after
measurement, and that superposition would be exactly the same as the
eigenstate obtained when one expanded in the aligned basis. So using a
different basis merely complicates the calculation, it doesn't actually
change anything. It is like trying to drive from Melbourne to Sydney using
a map based on an orthographic projection based on Brisbane. You might
manage it, but it would be needlessly difficult.

I am sorry that I have had to spend so much time on

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 7/06/2017 10:38 pm, Bruno Marchal wrote:

On 07 Jun 2017, at 11:42, Bruce Kellett wrote:
On 7/06/2017 7:09 pm, Bruno Marchal wrote:

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this 
morning and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome 
notation, but I will attempt to simplify as far as is possible. I 
will use '+' and '-' as spin states, rather than his 'left', 'right'.


He write the initial wave function as for the case when you and I 
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
   = |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and 
neither observer is split. But his fundamental mistake is already 
present.


A little test for you: what is wrong with the above set of 
equations from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-] 
means you have measured '-'.


He then claims that the QM results of perfect anticorrelation in 
the case of parallel polarizers has been recovered without any 
non-local interaction!


Spoiler -- in order to write the final line for |psi_1> he has 
already assumed collapse, when I measure '+', you are presented 
*only* with '-', so of course you get the right result -- he has 
built that non-locality in from the start.


?

From the start shows that it is local.


Your failure to see the problem here is symptomatic of your complete 
failure to understand EPR in the MWI.


I could say the same, but emphatic statements are not helping. My 
feeling is that you interpret the singlet state above like if it 
prepares Alice and Bob particles in the respective + and - states, but 
that is not the case. The singlet state describe a multiverse where 
Alice and Bob have all possible states, yet correlated.


The singlet state is rotationally invariant, yes, and can be expanded in 
any basis of the 2-d complex Hilbert space. That has never been in doubt.


Then in absence of collapse, all interactions, and results are 
obtained locally, and does not need to be correlated until they spread 
at low speed up their partners.


That does not follow. Although there are an infinity of possible bases 
for the singlet state, these are potential only, and do not exist in any 
operative sense until the state interacts with something that sets a 
direction. You appear to claim that A and B exist in separate worlds 
corresponding to each of this infinity of bases. But that is a 
misunderstanding. They are in superpositions in every base, sure, but 
that does not mean that there are 'worlds' corresponding to each 
possible base until some external interaction occurs. As you yourself 
have said, a world is something that is closed to interaction. But 
superpositions are not closed to interaction, they can interfere -- as 
in the two slit experiment, and essentially every other application of QM.


So there are no separate worlds corresponding to every possible 
orientation of the polarizers. Worlds can arise only after interaction 
and decoherence has progressed so that the overlap between the branches 
of the superposition is zero (FAPP if you like). It is only then that 
the branches can no longer interfere (interact) and are closed to 
interaction, and thus constitute different worlds.


The standard procedure in quantum mechanics when one is faced with a 
superposition that interacts with something external, is to expand the 
superposition in a base that corresponds to the external context. That 
is what happens when an unpolarized spin meets a polarizer aligned in a 
particular direction -- one expands the rotationally symmetric 
unpolarized state in the basis matching the external context. That is 
all that is happening with the singlet state above; when Alice comes to 
measure the symmetric state, it is convenient to expand the singlet 
state in a basis that corresponds to the orientation of Alice's 
polarizer. Then the result of the interaction is easily calculated. If 
one use some other basis, in some other direction, one would end up with 
a superposition of states after measurement, and that superposition 
would be exactly the same as the eigenstate obtained when one expanded 
in the aligned basis. So using a different basis merely complicates the 
calculation, it doesn't actually change anything. It is like trying to 
drive from Melbourne to Sydney using a map based on an orthographic 
projection based on Brisbane. You might manage it, but it would be 
needlessly difficult.


I am sorry that I have had to spend so much time on this diversion into 
Quantum Mechanics 101, but you seem determined to fail to understand the 
application of the most fundamental of quantum principles.


So, in the measurement of the singlet state

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 07 Jun 2017, at 11:42, Bruce Kellett wrote:


On 7/06/2017 7:09 pm, Bruno Marchal wrote:

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome  
notation, but I will attempt to simplify as far as is possible. I  
will use '+' and '-' as spin states, rather than his 'left',  
'right'.


He write the initial wave function as for the case when you and I  
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
   = |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and  
neither observer is split. But his fundamental mistake is already  
present.


A little test for you: what is wrong with the above set of  
equations from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-]  
means you have measured '-'.


He then claims that the QM results of perfect anticorrelation in  
the case of parallel polarizers has been recovered without any non- 
local interaction!


Spoiler -- in order to write the final line for |psi_1> he has  
already assumed collapse, when I measure '+', you are presented  
*only* with '-', so of course you get the right result -- he has  
built that non-locality in from the start.


?

From the start shows that it is local.


Your failure to see the problem here is symptomatic of your complete  
failure to understand EPR in the MWI.


I could say the same, but emphatic statements are not helping. My  
feeling is that you interpret the singlet state above like if it  
prepares Alice and Bob particles in the respective + and - states, but  
that is not the case. The singlet state describe a multiverse where  
Alice and Bob have all possible states, yet correlated. Then in  
absence of collapse, all interactions, and results are obtained  
locally, and does not need to be correlated until they spread at low  
speed up their partners.
Another argument is that the linear wave description is described by a  
differential equation which imposes locality, and make the non- 
locality only apparent in *all* branches (assuming the singlet state  
to be 100% pure). I agree it is weird that the "phase space is the  
real thing", but that is where the quantum weirdness comes from. Yet,  
the MWI just abandon the CFD, I don't see, in the Bell inequality  
violation any reason to believe that a influence at a distance should  
be called for.


Bruno



Until you can see why Price is wrong to claim locality in the above,  
you will never get this right, and you will continue to repeat the  
same errors time and time again.


Bruce

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 07 Jun 2017, at 04:25, Bruce Kellett wrote:


On 7/06/2017 5:51 am, Bruno Marchal wrote:


Here I found a not too bad paper on this subtle subject: 
https://arxiv.org/pdf/0902.3827.pdf
He do the calculus that different people have done sometimes. I  
mainly agree with it, but read it quickly.


His notation is somewhat difficult to follow. But it is instructive  
that footnote 36 comments that his treatment follows that of Price  
in the Everett FAQ. Since that derivation has been shown to assume  
non-locality "by the back door",


This is what you should elaborate on. I don't see that "non-locality"  
at all.




it follows that Baylock's derivation is equally flawed. Besides,  
Baylock does not actually derive the full result -- he omits to  
explicitly mention the step where Price assumes what amounts to a  
non-local influence. Baylock's equation 6, where he gets the 4  
possible combinations of results for the two experimenters, omits to  
calculate the relative probabilities of these sets of results, and  
it is those probabilities that can only be determined non-locally.


In each branch. But that is the "no-locality" which does not need an  
influence at a distance.





His discussion of counterfactual definiteness, and of its violation  
in MWI, is also flawed. He does not demonstrate that Bell actually  
uses CFD -- his treatment of CFD considers separate sequences of  
measurements, and then compares them. His criticism is that one of  
the sequences was not actually performed, so it cannot be assumed to  
give the QM result (could violate CFD).


But that is an entirely contrived situation. If you look at the  
original experimental papers, what Freedman and Clauser, Clauser,  
and Aspect et al., actually do is measure coincidence rates at  
various randomly set polarizer angles. They then compare coincidence  
rates at different angles -- they never use results from angles that  
were not actually measured! So whether CFD is true or not is totally  
irrelevant for the experiments.


In each branch!



They find violations of the relative coincidence rates expected if  
locality is assumed: CFD does not come into it; their results agree  
with QM at all relative angles.


As expected. The CFD is only use to get the action-at-a-distance.  
Without the CFD, we get non-locality, but without a physical action at  
a distance.


Bruno






Bruce

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 07 Jun 2017, at 11:31, Bruce Kellett wrote:


On 7/06/2017 7:09 pm, Bruno Marchal wrote:

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.


Have you a link. The webpage seems to be no more available at 
https://www.hedweb.com/manworld.htm


Maybe they took it down because they realized it was faulty!


If a webpage go down when there is something faulty, the net will soon  
be emptied!  :)





I did not go on-line because I saved a copy of this on my computer  
ages ago.


Me too. But I have been burgled since, and my computer, and the backup  
were stolen (in 2008). I forgot to re-download it.





I can forward the whole thing if you want,


It is not urgent. Especially that my current computer get senile. But  
thanks I will think about it in some future



but for the moment I attach Section Q32 where he covers EPR and  
locality.


Thank you, I will reread it.

Best,

Bruno





Bruce

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 7/06/2017 7:09 pm, Bruno Marchal wrote:

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this morning 
and was frankly appalled at the stupidity of what I saw.
Let me summarize briefly what he did. He has a very cumbersome 
notation, but I will attempt to simplify as far as is possible. I 
will use '+' and '-' as spin states, rather than his 'left', 'right'.


He write the initial wave function as for the case when you and I 
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
= |me, +,-,you> - |me,-,+,you>

He says that at this point no measurements have been made, and 
neither observer is split. But his fundamental mistake is already 
present.


A little test for you: what is wrong with the above set of equations 
from a no-collapse pov?


skipping some tedium, he then gets

|psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>

where the notation me[+] etc means I have measured '+', you[-] means 
you have measured '-'.


He then claims that the QM results of perfect anticorrelation in the 
case of parallel polarizers has been recovered without any non-local 
interaction!


Spoiler -- in order to write the final line for |psi_1> he has 
already assumed collapse, when I measure '+', you are presented 
*only* with '-', so of course you get the right result -- he has 
built that non-locality in from the start.


?

From the start shows that it is local.


Your failure to see the problem here is symptomatic of your complete 
failure to understand EPR in the MWI.
Until you can see why Price is wrong to claim locality in the above, you 
will never get this right, and you will continue to repeat the same 
errors time and time again.


Bruce

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 7/06/2017 7:09 pm, Bruno Marchal wrote:

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:

I have been through this before. I looked at Price again this morning 
and was frankly appalled at the stupidity of what I saw.


Have you a link. The webpage seems to be no more available at 
https://www.hedweb.com/manworld.htm


Maybe they took it down because they realized it was faulty!

I did not go on-line because I saved a copy of this on my computer ages 
ago. I can forward the whole thing if you want, but for the moment I 
attach Section Q32 where he covers EPR and locality.


Bruce

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Price_EPR.pdf
Description: Adobe PDF document

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 06 Jun 2017, at 01:23, Bruce Kellett wrote:


On 5/06/2017 8:42 pm, Bruno Marchal wrote:

On 05 Jun 2017, at 05:52, Bruce Kellett wrote:

On 5/06/2017 12:19 pm, Bruce Kellett wrote:

On 4/06/2017 10:05 pm, Bruno Marchal wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:


Your claim appears to be that Bell's theorem is not valid in MWI.


Bell's theorem is valid. His inequality does not even assume QM,  
but just locality.


I agree, but that is not what you were implying above. It seems  
that now you agree that the Bell inequalities assume only locality.


And a mono-universe, or a conservation of identity of Alice and Bob  
from the beginning to the end of the experience. But that is no  
more the case in the MWI. Everett explains already this when he  
introduces what will be called decoherence. Decpherence is local.


Believe it or not, those things are not relevant to the derivation  
of Bell's results. Besides, you simply contradict yourself -- you  
said exactly the opposite a line or two ago.


?






But these inequalities are violated by experiment.


Yes.

That can only mean that the assumption of locality was wrong --  
whatever interpretation of QM you adopt.


It means that locality and mono-universe cannot be maintained at  
once. But non-locality is not proved, unless you believe that Alice  
and Bob remains the same unique person all along, which is  
necessarlly not the case in the MWI of the EPR-Bell situation.


They split, but they retain identity in each branch.


Yes, and?





I think that this important part of recent exchanges might have  
got lost in the welter of to-and-fro.


Bruno accepts:

1. Bell's theorem (and the associated inequalities) are valid in  
MWI.
2. Bell's theorem assumes only locality (not even QM -- it is  
valid in classical physics also).


Locality, and identity preservation (or mono-universe, or  
counterfactual definiteness: all go away with Everett).


No, they do not. And these are not essential for Bell's derivation  
anyway.


Locality is assume for the Bell's inequality, and the mono-universe,  
or counterfactual definiteness is implicit, in both EPR and Bell.






3. The Aspect et al., and subsequent, experiments demonstrate that  
the Bell inequalities are violated.


Yes, but only from the points of view of one branch. But when we  
look how the singlet state is handled in the MWI, the correlation  
are apparent, but the results obtained by space-separated person  
does not need to be correlated, in some absolute sense, they need  
to be correlated with anyone interacting with both of them later,  
so that in all branches, it will look like if there has been an  
action at a distance, but all influence and information flows, and  
splitting, go at a speed lower than light.


It might have escaped your attention, but Alice and Bob need not be  
spacelike separated when they do their measurements on the spin  
singlet. For example, Bob could be at all times in Alice's forward  
light cone, so they are always in the same world -- as Alice splits  
with her measurement, Bob splits along with her,


In Alice branch. But Bob split Alice in his branch, and they do not  
need to be the same. There are few chance they could be the same.  
decoherence is local and spread at sub-light-speed.




so that when he does his measurement he is in the same world as  
Alice with her result as recorded in her lab book.


The two pairs of Alice and Bob can see that. There would be a non- 
local influence if there was only one pair, but they "doubly" split,  
to be short.





A lot of your prevarications over EPR stem from a failure to realize  
that spacelike separations are not essential


Indeed.



-- the proof is valid for *any* separation.


Absolutely.


Usually, spacelike is assumed only to assure the independence of the  
measurements made by Alice and Bob. But as long as they are truly  
independent, they can be at any separation.


OK.




It seems to follow with the force of simple logic that:

4. Experiment shows that QM is non-local, even in MWI.

Bruno appears to reject this conclusion. I conclude that Bruno's  
position is incoherent.


I will again ask you to tell me what is wrong with Michael Clive  
Price explanation ... except that the web page is not available.


I have been through this before. I looked at Price again this  
morning and was frankly appalled at the stupidity of what I saw.


Have you a link. The webpage seems to be no more available at 
https://www.hedweb.com/manworld.htm



Let me summarize briefly what he did. He has a very cumbersome  
notation, but I will attempt to simplify as far as is possible. I  
will use '+' and '-' as spin states, rather than his 'left', 'right'.


He write the initial wave function as for the case when you and I  
agree in advance to have aligned polarizers:


|psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
= |me, +,-,you> - |me,-,+,you>

He says that at this point no mea

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 7/06/2017 5:51 am, Bruno Marchal wrote:


Here I found a not too bad paper on this subtle subject: 
https://arxiv.org/pdf/0902.3827.pdf
He do the calculus that different people have done sometimes. I mainly 
agree with it, but read it quickly.


His notation is somewhat difficult to follow. But it is instructive that 
footnote 36 comments that his treatment follows that of Price in the 
Everett FAQ. Since that derivation has been shown to assume non-locality 
"by the back door", it follows that Baylock's derivation is equally 
flawed. Besides, Baylock does not actually derive the full result -- he 
omits to explicitly mention the step where Price assumes what amounts to 
a non-local influence. Baylock's equation 6, where he gets the 4 
possible combinations of results for the two experimenters, omits to 
calculate the relative probabilities of these sets of results, and it is 
those probabilities that can only be determined non-locally.


His discussion of counterfactual definiteness, and of its violation in 
MWI, is also flawed. He does not demonstrate that Bell actually uses CFD 
-- his treatment of CFD considers separate sequences of measurements, 
and then compares them. His criticism is that one of the sequences was 
not actually performed, so it cannot be assumed to give the QM result 
(could violate CFD).


But that is an entirely contrived situation. If you look at the original 
experimental papers, what Freedman and Clauser, Clauser, and Aspect et 
al., actually do is measure coincidence rates at various randomly set 
polarizer angles. They then compare coincidence rates at different 
angles -- they never use results from angles that were not actually 
measured! So whether CFD is true or not is totally irrelevant for the 
experiments. They find violations of the relative coincidence rates 
expected if locality is assumed: CFD does not come into it; their 
results agree with QM at all relative angles.


Bruce

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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 6 June 2017 at 01:46, Bruce Kellett  wrote:

> On 6/06/2017 10:21 am, David Nyman wrote:
>
> On 6 June 2017 at 00:23, Bruce Kellett < 
> bhkell...@optusnet.com.au> wrote:
>
>> On 5/06/2017 8:42 pm, Bruno Marchal wrote:
>>
>> I am not alone skeptical about inferring that the violation of the Bell
>>> inequalities shows action at a distance. What is wrong in Deutsch and
>>> Hayden? What is wrong in Rubin (Rubin, M.A. Found Phys Lett (2001) 14: 301.
>>> doi:10.1023/A:1012357515678), or in Maudlin's book?
>>>
>>
>> They don't all necessarily make the same mistake as Price, but they all
>> make equally silly mistakes, and build in the non-locality without
>> realizing it. Last year I analysed the argument by Tipler
>> (arxiv:quant-ph/0003146v1) in detail and showed where he made exactly this
>> mistake of building the non-locality in without realizing it.
>
>
> ​Bruce, I'm reading The Emergent Multiverse by David Wallace at the
> moment. He's well known as a prominent theorist of MWI. I don't know
> whether he falls under your definition of competence in this area, but as
> far as I've understood him, he fully accepts that MWI must be consistent
> with QM in all respects, including of course nonlocality.​ The distinction
> he makes is between nonlocality and the question of whether this requires
> us to think in terms of instantaneous transfer of information at
> greater-than-light speed, or "action at a distance". I can't say I've been
> able to get my head around his full exposition of this yet, but I'm pretty
> sure he doesn't  go along with your exposition of Price's seemingly faulty
> version of this.
>
>
> It is interesting that Wallace has come to this view. He, with Deutsch,
> was one of those who attempted to argue that MWI restored full locality.
> They also tried to derive the Born Rule from within MWI, and failed in that
> too.
>
> I do not know the book you refer to, but if Wallace now accepts that QM
> and Bell implies non-locality, then I fully agree. I have always argued, on
> this list and elsewhere, that non-locality does not mean the instantaneous
> transfer of physical information -- if you think about it, that would, in a
> sense, be a local, albeit FTL, effect. The core of the quantum singlet
> state is that it does not involve the physical positions of the particles.
> It is expressed in configuration space, and the difficulties appear to
> arise from interpreting configuration space as though it were the same as
> ordinary 3-space. What has been said is that the singlet state is always
> local in configuration space, which translates to non-locality in 3-space.
> And this without some FTL information transfer. If there were FTL
> information transfer, then that could be manipulated to give FTL
> signalling, and there are all sorts of theorems in QM that show that FTL
> signalling is not possible.
>
> But it seems as though Wallace is coming to see these things as do the
> majority of other physicists -- non-locality is intrinsic to quantum
> entanglement.
>

​Wallace uses the term non-separability. ​He makes an analogy, to a certain
extent, with the ontology of field theories such as electromagnetism, about
which he says "The structural complexity of a given electromagnetic field
is represented not in the properties of very small spacetime regions
(indeed in the limit as these regions become point sized, the field's
structure becomes almost trivial) but in the way in which those properties
vary across spacetime. Furthermore, this general model is characteristic of
pretty much any classical field theory, except that vector fields seem
mathematically tame compared to the sorts of mathematical objects used to
represent the field values of many classical field theories.". He gives a
number of examples of these latter objects including the affine connections
of General Relativity. He then goes on from this analogy to propose an
ontology for quantum field theory which he calls Spacetime State Realism. I
can't really attempt to elaborate on this here.

Moving on this basis to the question "Does Everettian quantum mechanics
display action at a distance?" he answers in the negative. He justifies
this by elaborating on the observation that "In a quantum field theory, the
quantum state of any region depends on the quantum state of some cross
section of the past light cone of that region. Disturbances cannot
propagate into that light cone." To the question "Does Everettian quantum
mechanics display non-separability?" he answers in the positive. He
justifies this by elaborating on the observation that "Because of
entanglement, knowing the density operators of regions A and B does not
suffice to fix the density operator of (the union of) A and B. Some of the
properties of (the union of) A and B are genuinely non-local: they have
local physical manifestations only if we arrange appropriate dynamics.".

I can't do justice to his exposition of the above positions in the full
text, but they seem reason

Re: A thought on MWI and its alternative(s)

[Alan McKenzie]

I am completely new to Google Groups, and so I hope you may understand if 
my intrusion here is inappropriate or if I break any protocols in replying 
to this topic. I came across this Group while searching for a paper.

 

I was very taken by Pierz’s first statement, as it reminded me of my own 
agonies over the seeming incompatibility between (1) the block universe 
where all events (some of which we perceive as “in the future”, depending 
upon our motion relative to the events) are “frozen” into the space-time 
fabric, and (2) quantum uncertainty about future events.

 

(In case any of the many physicists who do not accept the block universe 
are reading this, perhaps I can refer them to “Proposal for an experiment 
to determine the block universe” (http://arxiv.org/abs/1603.08959) in which 
the Mars Reconnaissance Orbiter will play a key role…)

 

Quantum uncertainty, of course, is fundamental in that there are events 
whose outcomes cannot be predicted with 100 per cent certainty in this 
universe.  Pierz is on the right track in saying that the Many-Worlds model 
may address this uncertainty, changing the question to one of uncertainty 
over which branch of the Many-Worlds tree one is in. (Of course, we inhabit 
many “parallel” branches, although each version of us perceives ourself to 
be unique.)

 

The difficulty with the Many Worlds Interpretation has always been that 
branching is incompatible with the block-universe model. How can a block 
universe have branches? The proposal of this paper – 
http://arxiv.org/abs/1602.04247  (“Some remarks on the mathematical 
structure of the multiverse”) and described more completely in 
http://arxiv.org/abs/1609.04050  (“A discrete, finite multiverse”) – gets 
round that difficulty. Each branch of the Many-Worlds tree comprises many 
(but not infinitely many) “filaments”, each extending from the trunk to the 
topmost twig.  Each one of these filaments is a block universe.  Events in 
these universes tend to be similar towards the trunk and tend to diverge as 
one proceeds up towards the thinner branches.

 

Of course, this hypothesis only makes sense if the multiverse is purely a 
system of mathematical relations, in the Tegmark sense. (However, Tegmark’s 
model is ultimately incompatible with the hypothesis: see, for instance, 
the discussion in http://www.godel-universe.com/tegmark/).


On Friday, May 26, 2017 at 2:30:07 AM UTC+1, Pierz wrote:
>
> Recently I've been studying a lot of history, and I've often thought about 
> how, according to special relativity, you can translate time into space and 
> vice versa...
>
 

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 05 Jun 2017, at 19:09, David Nyman wrote:


On 5 June 2017 at 17:38, Bruno Marchal  wrote:

On 05 Jun 2017, at 15:48, David Nyman wrote:


On 5 June 2017 at 14:22, Bruno Marchal  wrote:

On 04 Jun 2017, at 14:48, David Nyman wrote:




On 4 Jun 2017 1:05 p.m., "Bruno Marchal"  wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:

On 1/06/2017 10:19 pm, Bruno Marchal wrote:
On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:
On 31 May 2017, at 04:01, Bruce Kellett wrote:
On 30/05/2017 9:35 pm, Bruno Marchal wrote:
On 30 May 2017, at 11:28, Telmo Menezes wrote:

snip


Your claim appears to be that Bell's theorem is not valid in MWI.

Bell's theorem is valid. His inequality does not even assume QM,  
but just locality. It is violate when we do the experience, like  
Aspect, and this shows non-locality in our branch, but when  
looking at the big picture, we see that this non-locality has a  
local origin. It would need an action at a distance to destroy the  
alternante branches alwailable to Bob, but without collapse, non- 
locality is a local, branch-owned, phenomenon. I take Bells  
theorem + Aspect as a quasi definite proof that if there is one  
universe, then there are many universes.







This is nonsense. Bell's theorem is a theorem of quantum  
mechanics, and it is therefore valid in all interpretations of  
that theory.


Yes, in all interpretation of quantum mechanics, the relevant  
branches violate the inequality, but they do that without  
involving an action at a distance when we look at the entire wave.  
It is phenomenological.


Suppose one were to enquire what makes those branches "relevant".  
One answer is that other pairings would be in conflict both with  
the predictions of QM and with observation, but that is circular.  
What then? Perhaps one might speculate that other pairings would  
somehow be fundamentally inconsistent with any physics that would  
permit its own coherent (or for that matter decoherent) observation.


The branches are just the superposed states, and with singlet or  
with simple qubit, the other branches are just the other term of  
the superposition which describes ourselves. To get rid of such  
superposition, we need to get rid of quantum mechanics, *and* of  
mechanism.


​I'm not sure I made myself clear. What I meant by "other  
pairings"​ was the ones we never expect to witness - e.g. the ones  
that presumably might not violate Bell's inequalities.


OK. You mean this in the context of assuming quantum mechanics. If  
we say that we don't see them because QM disallows them, or because  
things just aren't that way, that is circular.


I am not sure I understand this. If we assume QM, it is standard.  
Unlike Mechanism, somehow QM solves the measure problem.


So is the idea then that all possible 'measurements that Alice and  
Bob could possibly make are already 'paired', in terms of  
superpositions, in the MWI view?




Yes. The MW view of the singlet state (up down + down up) is a multi- 
relative states, or multiverse, where Alice is in front of any well  
defined up' and Bob has the well paired corresponding down'. As there  
is a continuum of angular values for up, it describes 2^aleph_0 pairs  
of Alice and Bob, with maxiamlly correlated spin.







And then the question of which branch either of them is situated in,  
and consequently which pairing they will be associated with, is  
determined by the measurement subsequently performed (apparently  
individually) by each of them?


Yes.

The amazing thing, eventually due to the trigonometric pythagorean  
identity, that sin^2(theta) + cos^2(theta) = 1, + Born rules, makes  
each branch violates the Bell's inequality, but there is no non local  
influence that I can see, it is apparent because we abstract from all  
Alice and Bob, and possible third parties involved.


Here I found a not too bad paper on this subtle subject: 
https://arxiv.org/pdf/0902.3827.pdf
He do the calculus that different people have done sometimes. I mainly  
agree with it, but read it quickly.




ISTM that saying it's "just the other term of the superposition  
which describes ourselves" is equally circular. What about  
superpositions that don't "describe ourselves"?


With Copenhagen, all superposition don't describe the observers, and  
we get standard QM with collapse. Then with Everett, we have an  
explanation why, even without collapse, the average observer, when  
doing a measurement, entangled itself and correlate his brain with  
the outcome, and the proba are justify by the FPI. may be I still  
miss something?


(here, by superposition which describes ourself, I meant only  
something like (me -- cat alive + me -- cat dead).


So my question was about whether there is a non-circular answer to  
the question of why we don't expect observations by Alice and Bob  
to lead to the correlation of such 'malformed' pairs. Perhaps  
because such correlation might entail a 

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 6/06/2017 10:21 am, David Nyman wrote:
On 6 June 2017 at 00:23, Bruce Kellett > wrote:


On 5/06/2017 8:42 pm, Bruno Marchal wrote:

I am not alone skeptical about inferring that the violation of
the Bell inequalities shows action at a distance. What is
wrong in Deutsch and Hayden? What is wrong in Rubin (Rubin,
M.A. Found Phys Lett (2001) 14: 301.
doi:10.1023/A:1012357515678), or in Maudlin's book?


They don't all necessarily make the same mistake as Price, but
they all make equally silly mistakes, and build in the
non-locality without realizing it. Last year I analysed the
argument by Tipler (arxiv:quant-ph/0003146v1) in detail and showed
where he made exactly this mistake of building the non-locality in
without realizing it. 



​Bruce, I'm reading The Emergent Multiverse by David Wallace at the 
moment. He's well known as a prominent theorist of MWI. I don't know 
whether he falls under your definition of competence in this area, but 
as far as I've understood him, he fully accepts that MWI must be 
consistent with QM in all respects, including of course nonlocality.​ 
The distinction he makes is between nonlocality and the question of 
whether this requires us to think in terms of instantaneous transfer 
of information at greater-than-light speed, or "action at a distance". 
I can't say I've been able to get my head around his full exposition 
of this yet, but I'm pretty sure he doesn't  go along with your 
exposition of Price's seemingly faulty version of this.


It is interesting that Wallace has come to this view. He, with Deutsch, 
was one of those who attempted to argue that MWI restored full locality. 
They also tried to derive the Born Rule from within MWI, and failed in 
that too.


I do not know the book you refer to, but if Wallace now accepts that QM 
and Bell implies non-locality, then I fully agree. I have always argued, 
on this list and elsewhere, that non-locality does not mean the 
instantaneous transfer of physical information -- if you think about it, 
that would, in a sense, be a local, albeit FTL, effect. The core of the 
quantum singlet state is that it does not involve the physical positions 
of the particles. It is expressed in configuration space, and the 
difficulties appear to arise from interpreting configuration space as 
though it were the same as ordinary 3-space. What has been said is that 
the singlet state is always local in configuration space, which 
translates to non-locality in 3-space. And this without some FTL 
information transfer. If there were FTL information transfer, then that 
could be manipulated to give FTL signalling, and there are all sorts of 
theorems in QM that show that FTL signalling is not possible.


But it seems as though Wallace is coming to see these things as do the 
majority of other physicists -- non-locality is intrinsic to quantum 
entanglement.


As we know, MWI hypothesises multiple outcomes for each measurement 
event. So on this basis, when Alice makes a measurement there is an 
immediate split into branches consistent both with the measurement she 
records and with its counterfactual partner. The same considerations 
must apply equally to Bob. So we now have a spectrum of available 
branches in which exist potential pairings of recorded measurements 
that would be consistent with QM. The question then concerns which 
pairings of Alice and Bob we (or they) should expect to observe in the 
form of actual encounters for the purpose of comparing notes. QM tells 
us that the results of any such observable pairings must be consistent 
with violation of Bell's inequalities. Can we say, in terms of the 
logic of MWI, why this might be so?


Yes. This is essentially the Tipler calculation that I have summarized 
elsewhere. It is non-local, but it shows how the different branches 
arising from each measurement must always match up to give the correct 
correlations. Conceptually, what goes on is easier to understand if you 
consider an EPR experiment at time-like separations. Then Bob can always 
be in Alice's forward light cone, and there is no ambiguity as to what 
splits occur, and when they occur.


Bruce

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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 6 June 2017 at 00:23, Bruce Kellett  wrote:

> On 5/06/2017 8:42 pm, Bruno Marchal wrote:
>
>> On 05 Jun 2017, at 05:52, Bruce Kellett wrote:
>>
>>> On 5/06/2017 12:19 pm, Bruce Kellett wrote:
>>>
 On 4/06/2017 10:05 pm, Bruno Marchal wrote:

> On 02 Jun 2017, at 03:01, Bruce Kellett wrote:
>
> Your claim appears to be that Bell's theorem is not valid in MWI.
>>
>
> Bell's theorem is valid. His inequality does not even assume QM, but
> just locality.
>

 I agree, but that is not what you were implying above. It seems that
 now you agree that the Bell inequalities assume only locality.

>>>
>> And a mono-universe, or a conservation of identity of Alice and Bob from
>> the beginning to the end of the experience. But that is no more the case in
>> the MWI. Everett explains already this when he introduces what will be
>> called decoherence. Decpherence is local.
>>
>
> Believe it or not, those things are not relevant to the derivation of
> Bell's results. Besides, you simply contradict yourself -- you said exactly
> the opposite a line or two ago.
>
> But these inequalities are violated by experiment.

>>>
>> Yes.
>>
>> That can only mean that the assumption of locality was wrong -- whatever
 interpretation of QM you adopt.

>>>
>> It means that locality and mono-universe cannot be maintained at once.
>> But non-locality is not proved, unless you believe that Alice and Bob
>> remains the same unique person all along, which is necessarlly not the case
>> in the MWI of the EPR-Bell situation.
>>
>
> They split, but they retain identity in each branch.
>
> I think that this important part of recent exchanges might have got lost
>>> in the welter of to-and-fro.
>>>
>>> Bruno accepts:
>>>
>>> 1. Bell's theorem (and the associated inequalities) are valid in MWI.
>>> 2. Bell's theorem assumes only locality (not even QM -- it is valid in
>>> classical physics also).
>>>
>>
>> Locality, and identity preservation (or mono-universe, or counterfactual
>> definiteness: all go away with Everett).
>>
>
> No, they do not. And these are not essential for Bell's derivation anyway.
>
> 3. The Aspect et al., and subsequent, experiments demonstrate that the
>>> Bell inequalities are violated.
>>>
>>
>> Yes, but only from the points of view of one branch. But when we look how
>> the singlet state is handled in the MWI, the correlation are apparent, but
>> the results obtained by space-separated person does not need to be
>> correlated, in some absolute sense, they need to be correlated with anyone
>> interacting with both of them later, so that in all branches, it will look
>> like if there has been an action at a distance, but all influence and
>> information flows, and splitting, go at a speed lower than light.
>>
>
> It might have escaped your attention, but Alice and Bob need not be
> spacelike separated when they do their measurements on the spin singlet.
> For example, Bob could be at all times in Alice's forward light cone, so
> they are always in the same world -- as Alice splits with her measurement,
> Bob splits along with her, so that when he does his measurement he is in
> the same world as Alice with her result as recorded in her lab book.
>
> A lot of your prevarications over EPR stem from a failure to realize that
> spacelike separations are not essential -- the proof is valid for *any*
> separation. Usually, spacelike is assumed only to assure the independence
> of the measurements made by Alice and Bob. But as long as they are truly
> independent, they can be at any separation.
>
> It seems to follow with the force of simple logic that:
>>>
>>> 4. Experiment shows that QM is non-local, even in MWI.
>>>
>>> Bruno appears to reject this conclusion. I conclude that Bruno's
>>> position is incoherent.
>>>
>>
>> I will again ask you to tell me what is wrong with Michael Clive Price
>> explanation ... except that the web page is not available.
>>
>
> I have been through this before. I looked at Price again this morning and
> was frankly appalled at the stupidity of what I saw. Let me summarize
> briefly what he did. He has a very cumbersome notation, but I will attempt
> to simplify as far as is possible. I will use '+' and '-' as spin states,
> rather than his 'left', 'right'.
>
> He write the initial wave function as for the case when you and I agree in
> advance to have aligned polarizers:
>
> |psi_1> = }me, electrons,you> = |me>(|+-> - |-+>)|you>
>  = |me, +,-,you> - |me,-,+,you>
>
> He says that at this point no measurements have been made, and neither
> observer is split. But his fundamental mistake is already present.
>
> A little test for you: what is wrong with the above set of equations from
> a no-collapse pov?
>
> skipping some tedium, he then gets
>
> |psi_3> = |me[+],+,-,you[-]> - |me[-],-,+,you[+]>
>
> where the notation me[+] etc means I have measured '+', you[-] means you
> have measured '-'.
>
> He then claims that the QM

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 5 June 2017 at 17:38, Bruno Marchal  wrote:

>
> On 05 Jun 2017, at 15:48, David Nyman wrote:
>
> On 5 June 2017 at 14:22, Bruno Marchal  wrote:
>
>>
>> On 04 Jun 2017, at 14:48, David Nyman wrote:
>>
>>
>>
>> On 4 Jun 2017 1:05 p.m., "Bruno Marchal"  wrote:
>>
>>
>> On 02 Jun 2017, at 03:01, Bruce Kellett wrote:
>>
>> On 1/06/2017 10:19 pm, Bruno Marchal wrote:
>>>
 On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
 On 1/06/2017 4:43 am, Bruno Marchal wrote:

> On 31 May 2017, at 04:01, Bruce Kellett wrote:
>>
>>> On 30/05/2017 9:35 pm, Bruno Marchal wrote:
>>>
 On 30 May 2017, at 11:28, Telmo Menezes wrote:

 snip


>>
>>> Your claim appears to be that Bell's theorem is not valid in MWI.
>>>
>>
>> Bell's theorem is valid. His inequality does not even assume QM, but just
>> locality. It is violate when we do the experience, like Aspect, and this
>> shows non-locality in our branch, but when looking at the big picture, we
>> see that this non-locality has a local origin. It would need an action at a
>> distance to destroy the alternante branches alwailable to Bob, but without
>> collapse, non-locality is a local, branch-owned, phenomenon. I take Bells
>> theorem + Aspect as a quasi definite proof that if there is one universe,
>> then there are many universes.
>>
>>
>>
>>
>>
>>
>> This is nonsense. Bell's theorem is a theorem of quantum mechanics, and
>>> it is therefore valid in all interpretations of that theory.
>>>
>>
>> Yes, in all interpretation of quantum mechanics, the relevant branches
>> violate the inequality, but they do that without involving an action at a
>> distance when we look at the entire wave. It is phenomenological.
>>
>>
>> Suppose one were to enquire what makes those branches "relevant". One
>> answer is that other pairings would be in conflict both with the
>> predictions of QM and with observation, but that is circular. What then?
>> Perhaps one might speculate that other pairings would somehow be
>> fundamentally inconsistent with any physics that would permit its own
>> coherent (or for that matter decoherent) observation.
>>
>>
>> The branches are just the superposed states, and with singlet or with
>> simple qubit, the other branches are just the other term of the
>> superposition which describes ourselves. To get rid of such superposition,
>> we need to get rid of quantum mechanics, *and* of mechanism.
>>
>
> ​I'm not sure I made myself clear. What I meant by "other pairings"​ was
> the ones we never expect to witness - e.g. the ones that presumably might
> not violate Bell's inequalities.
>
>
> OK. You mean this in the context of assuming quantum mechanics. If we say
> that we don't see them because QM disallows them, or because things just
> aren't that way, that is circular.
>

> I am not sure I understand this. If we assume QM, it is standard. Unlike
> Mechanism, somehow QM solves the measure problem.
>

So is the idea then that all possible 'measurements that Alice and Bob
could possibly make are already 'paired', in terms of superpositions, in
the MWI view? And then the question of which branch either of them is
situated in, and consequently which pairing they will be associated with,
is determined by the measurement subsequently performed (apparently
individually) by each of them?

ISTM that saying it's "just the other term of the superposition which
> describes ourselves" is equally circular. What about superpositions that
> don't "describe ourselves"?
>
>
> With Copenhagen, all superposition don't describe the observers, and we
> get standard QM with collapse. Then with Everett, we have an explanation
> why, even without collapse, the average observer, when doing a measurement,
> entangled itself and correlate his brain with the outcome, and the proba
> are justify by the FPI. may be I still miss something?
>

> (here, by superposition which describes ourself, I meant only something
> like (me -- cat alive + me -- cat dead).
>
> So my question was about whether there is a non-circular answer to the
> question of why we don't expect observations by Alice and Bob to lead to
> the correlation of such 'malformed' pairs. Perhaps because such correlation
> might entail a 'physics' that precluded the act of observation itself.
>
>
> I am not sure what you are asking. If we suppose QM, the reason why the
> "malformed pair" are not seen is that QM disallow them, or makes them very
> rare.
> If we don't suppose QM, like when assuming mechanism, we have to derive
> QM, or the correct theory in case QM is incorrect, to answer this.
>
> But the context here was the question "does the abandon of the collapse
> prevents influence at a distance". Bruce claims it does not, and me (but
> here there are many others, even on this list) claims it does, or at the
> least, that we cannot use the Bell violation to claim MWI is not local. In
> that thread we fully assume QM (without collapse).
>

​I think I follow. Wallace, 

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 05 Jun 2017, at 15:48, David Nyman wrote:


On 5 June 2017 at 14:22, Bruno Marchal  wrote:

On 04 Jun 2017, at 14:48, David Nyman wrote:




On 4 Jun 2017 1:05 p.m., "Bruno Marchal"  wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:

On 1/06/2017 10:19 pm, Bruno Marchal wrote:
On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:
On 31 May 2017, at 04:01, Bruce Kellett wrote:
On 30/05/2017 9:35 pm, Bruno Marchal wrote:
On 30 May 2017, at 11:28, Telmo Menezes wrote:

snip


Your claim appears to be that Bell's theorem is not valid in MWI.

Bell's theorem is valid. His inequality does not even assume QM,  
but just locality. It is violate when we do the experience, like  
Aspect, and this shows non-locality in our branch, but when looking  
at the big picture, we see that this non-locality has a local  
origin. It would need an action at a distance to destroy the  
alternante branches alwailable to Bob, but without collapse, non- 
locality is a local, branch-owned, phenomenon. I take Bells theorem  
+ Aspect as a quasi definite proof that if there is one universe,  
then there are many universes.







This is nonsense. Bell's theorem is a theorem of quantum mechanics,  
and it is therefore valid in all interpretations of that theory.


Yes, in all interpretation of quantum mechanics, the relevant  
branches violate the inequality, but they do that without involving  
an action at a distance when we look at the entire wave. It is  
phenomenological.


Suppose one were to enquire what makes those branches "relevant".  
One answer is that other pairings would be in conflict both with  
the predictions of QM and with observation, but that is circular.  
What then? Perhaps one might speculate that other pairings would  
somehow be fundamentally inconsistent with any physics that would  
permit its own coherent (or for that matter decoherent) observation.


The branches are just the superposed states, and with singlet or  
with simple qubit, the other branches are just the other term of the  
superposition which describes ourselves. To get rid of such  
superposition, we need to get rid of quantum mechanics, *and* of  
mechanism.


​I'm not sure I made myself clear. What I meant by "other  
pairings"​ was the ones we never expect to witness - e.g. the ones  
that presumably might not violate Bell's inequalities.


OK. You mean this in the context of assuming quantum mechanics.



If we say that we don't see them because QM disallows them, or  
because things just aren't that way, that is circular.


I am not sure I understand this. If we assume QM, it is standard.  
Unlike Mechanism, somehow QM solves the measure problem.




ISTM that saying it's "just the other term of the superposition  
which describes ourselves" is equally circular. What about  
superpositions that don't "describe ourselves"?


With Copenhagen, all superposition don't describe the observers, and  
we get standard QM with collapse. Then with Everett, we have an  
explanation why, even without collapse, the average observer, when  
doing a measurement, entangled itself and correlate his brain with the  
outcome, and the proba are justify by the FPI. may be I still miss  
something?


(here, by superposition which describes ourself, I meant only  
something like (me -- cat alive + me -- cat dead).






So my question was about whether there is a non-circular answer to  
the question of why we don't expect observations by Alice and Bob to  
lead to the correlation of such 'malformed' pairs. Perhaps because  
such correlation might entail a 'physics' that precluded the act of  
observation itself.


I am not sure what you are asking. If we suppose QM, the reason why  
the "malformed pair" are not seen is that QM disallow them, or makes  
them very rare.
If we don't suppose QM, like when assuming mechanism, we have to  
derive QM, or the correct theory in case QM is incorrect, to answer  
this.


But the context here was the question "does the abandon of the  
collapse prevents influence at a distance". Bruce claims it does not,  
and me (but here there are many others, even on this list) claims it  
does, or at the least, that we cannot use the Bell violation to claim  
MWI is not local. In that thread we fully assume QM (without collapse).







This might ultimately be related to the speculation that the  
appearance of spacetime itself may emerge as a consequence of  
entanglement.



Possibly, although you might elaborate a little bit.

​Well, my (admittedly vague) speculation was that the  
'entanglements'​ we never expect to observe might be 'malformed' in  
some way that precluded the emergence of a spacetime within which  
such observation could occur.


It is a bit vague indeed. I think our allusion between space and  
entanglement is related to some approach trying to derive the space- 
time-gravity structure of the physical universe from the quantum  
entanglement. I am far away to be fa

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 5 June 2017 at 14:22, Bruno Marchal  wrote:

>
> On 04 Jun 2017, at 14:48, David Nyman wrote:
>
>
>
> On 4 Jun 2017 1:05 p.m., "Bruno Marchal"  wrote:
>
>
> On 02 Jun 2017, at 03:01, Bruce Kellett wrote:
>
> On 1/06/2017 10:19 pm, Bruno Marchal wrote:
>>
>>> On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
>>> On 1/06/2017 4:43 am, Bruno Marchal wrote:
>>>
 On 31 May 2017, at 04:01, Bruce Kellett wrote:
>
>> On 30/05/2017 9:35 pm, Bruno Marchal wrote:
>>
>>> On 30 May 2017, at 11:28, Telmo Menezes wrote:
>>>
>>> I get your point with decoherence.
 Again, I would say that it all depends on theories of mind. What
 does
 mind supervene on? Perhaps it is true that every single coupling
 with
 the environment prevents the current observer state to become
 compatible with other branches. But can we be sure? I feel that such
 certainties come from a strong belief in emergentism (which I cannot
 disprove, but find problematic).

>>>
>>> It is impossible to recohere the past, FAPP.
>>>
>>> But only FAPP. To make the blue T-rex interfereing with the
>>> red-T-rex, we must erase the trace of particle interaction between the
>>> T-rex in its whole light-cone, and this without forgetting the particles
>>> "swallowed" by the black-holes, etc. It is just completely impossible, 
>>> but
>>> to derive from that the unicity of the past, is, it seems to me (and 
>>> you if
>>> I understood well) is invalid.
>>>
>>
>> I think the recoherence of paths that have completely decohered is
>> more than just FAPP impossible, I think it is impossible in principle. 
>> One
>> major problem with recoherence in general is that information leaks from
>> the paths at the speed of light (as well as less slowly for other
>> interactions). Since this vital information goes out along the light 
>> cone,
>> it can never be recaptured and returned to the original interaction.
>>
>
> In QM + special relativity OK. (note that to me QM + special
> relativity => no collapse (and even the Many dreams, but we have agreed to
> disagree on this if I remember well).
>

 Reasoning in QM without SR is not very profitable. Besides, QM + SR
 does not particularly imply MWI -- it is perfectly possible to have a
 consistent collapse model of QM+SR. I know you don't agree because of the
 non-locality implied by EPR, but this non-locality is not removed in MWI,
 regardless of what you might say.

>>>
>>> I don't see it, and the mast time we discuss this, we conclude on some
>>> vocabulary problem. When there is no collapse, measurement tells to people
>>> light separated in which branch theiy belongs, but to exploits that
>>> information, they need to come into contact.
>>>
>>
>> Last time we discussed this, no resolution was achieved.
>>
>
> That is not what I remembered, but I will not insist.
>
>
>
>
>
> In QM, with or without collapse, decoherence and the transition from the
>> pure state to a mixture gives a definite measurement result.
>>
>
> In particular branches only. When looking at the whole wave including the
> observers, decoherence explain why it *looks*, to all observers in the
> different branches, that mixed states have been obtained, but that is not
> the case in the global description.
>
>
>
>
>
> Without collapse, different branches get different results, but once
>> obtained, these results are fixed, and are not affected by whether Alice
>> and Bob exchange information or not.
>>
>
> I agree. That is used in the fact that in EPR like situation, when Alice
> and Bob are space-time separated, what we have is "only" an infinity of
> Alices and Bobs, all with their spin correlated, and when Alice makes her
> measurement, at any angle, she will know Bob's possible result, without
> needing any action at a distance. She just localize herself, and her
> corresponding Bob, in which branch they belong. There is no influence at a
> distance, although we would need it to talk of token unique Alice and Bob
> in case there would be only one universe.
>
>
>
>
>
>> Consequently, indispensable phase information is lost *in principle*, so
>> the recoherence is, in general, impossible.
>>
>
> OK. (I was reasoning in naive classical QM)
>
> Of course, with carefully constructed systems, where the loss of
>> information along the light cone is prevented, recoherence is possible in
>> special circumstances, but not in general.
>>
>> From this, the uniqueness of the past of any decoherent history is
>> assured. So deriving the unicity (if I understand this use of the word) 
>> is
>> by no means invalid -- it is proved.
>>
>
> In QM + SR. OK.
>
> Even if one encounters one of those rare situations in which
>> recoherence is achieved, that still does not in

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 04 Jun 2017, at 14:48, David Nyman wrote:




On 4 Jun 2017 1:05 p.m., "Bruno Marchal"  wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:

On 1/06/2017 10:19 pm, Bruno Marchal wrote:
On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:
On 31 May 2017, at 04:01, Bruce Kellett wrote:
On 30/05/2017 9:35 pm, Bruno Marchal wrote:
On 30 May 2017, at 11:28, Telmo Menezes wrote:

I get your point with decoherence.
Again, I would say that it all depends on theories of mind. What does
mind supervene on? Perhaps it is true that every single coupling with
the environment prevents the current observer state to become
compatible with other branches. But can we be sure? I feel that such
certainties come from a strong belief in emergentism (which I cannot
disprove, but find problematic).

It is impossible to recohere the past, FAPP.

But only FAPP. To make the blue T-rex interfereing with the red-T- 
rex, we must erase the trace of particle interaction between the T- 
rex in its whole light-cone, and this without forgetting the  
particles "swallowed" by the black-holes, etc. It is just completely  
impossible, but to derive from that the unicity of the past, is, it  
seems to me (and you if I understood well) is invalid.


I think the recoherence of paths that have completely decohered is  
more than just FAPP impossible, I think it is impossible in  
principle. One major problem with recoherence in general is that  
information leaks from the paths at the speed of light (as well as  
less slowly for other interactions). Since this vital information  
goes out along the light cone, it can never be recaptured and  
returned to the original interaction.


In QM + special relativity OK. (note that to me QM + special  
relativity => no collapse (and even the Many dreams, but we have  
agreed to disagree on this if I remember well).


Reasoning in QM without SR is not very profitable. Besides, QM + SR  
does not particularly imply MWI -- it is perfectly possible to have  
a consistent collapse model of QM+SR. I know you don't agree because  
of the non-locality implied by EPR, but this non-locality is not  
removed in MWI, regardless of what you might say.


I don't see it, and the mast time we discuss this, we conclude on  
some vocabulary problem. When there is no collapse, measurement  
tells to people light separated in which branch theiy belongs, but  
to exploits that information, they need to come into contact.


Last time we discussed this, no resolution was achieved.

That is not what I remembered, but I will not insist.





In QM, with or without collapse, decoherence and the transition from  
the pure state to a mixture gives a definite measurement result.


In particular branches only. When looking at the whole wave  
including the observers, decoherence explain why it *looks*, to all  
observers in the different branches, that mixed states have been  
obtained, but that is not the case in the global description.






Without collapse, different branches get different results, but once  
obtained, these results are fixed, and are not affected by whether  
Alice and Bob exchange information or not.


I agree. That is used in the fact that in EPR like situation, when  
Alice and Bob are space-time separated, what we have is "only" an  
infinity of Alices and Bobs, all with their spin correlated, and  
when Alice makes her measurement, at any angle, she will know Bob's  
possible result, without needing any action at a distance. She just  
localize herself, and her corresponding Bob, in which branch they  
belong. There is no influence at a distance, although we would need  
it to talk of token unique Alice and Bob in case there would be only  
one universe.






Consequently, indispensable phase information is lost *in  
principle*, so the recoherence is, in general, impossible.


OK. (I was reasoning in naive classical QM)

Of course, with carefully constructed systems, where the loss of  
information along the light cone is prevented, recoherence is  
possible in special circumstances, but not in general.


From this, the uniqueness of the past of any decoherent history is  
assured. So deriving the unicity (if I understand this use of the  
word) is by no means invalid -- it is proved.


In QM + SR. OK.

Even if one encounters one of those rare situations in which  
recoherence is achieved, that still does not invalidate the  
uniqueness of the past history -- recoherence, if it occurs, simply  
means that no new branches are formed at that point, so the  
decoherent history remains unique.


OK. That might suggest that we identify our indistinguishible past  
in arithmetic, if we assume mechanism. I use the Y = II principle,  
or the "quantum" linearity of the tensor product "@": we have that   
a @ (b + c) = (a @ b) + (a @ c).


That makes sense.

Linearity is the heart of QM. It is linearity that allows  
superpositions, and leads to all the "quantum weirdness"

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 05 Jun 2017, at 05:52, Bruce Kellett wrote:


On 5/06/2017 12:19 pm, Bruce Kellett wrote:

On 4/06/2017 10:05 pm, Bruno Marchal wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:


Your claim appears to be that Bell's theorem is not valid in MWI.


Bell's theorem is valid. His inequality does not even assume QM,  
but just locality.


I agree, but that is not what you were implying above. It seems  
that now you agree that the Bell inequalities assume only locality.


And a mono-universe, or a conservation of identity of Alice and Bob  
from the beginning to the end of the experience. But that is no more  
the case in the MWI. Everett explains already this when he introduces  
what will be called decoherence. Decpherence is local.





But these inequalities are violated by experiment.


Yes.



That can only mean that the assumption of locality was wrong --  
whatever interpretation of QM you adopt.


It means that locality and mono-universe cannot be maintained at once.  
But non-locality is not proved, unless you believe that Alice and Bob  
remains the same unique person all along, which is necessarlly not the  
case in the MWI of the EPR-Bell situation.







I think that this important part of recent exchanges might have got  
lost in the welter of to-and-fro.


Bruno accepts:

1. Bell's theorem (and the associated inequalities) are valid in MWI.
2. Bell's theorem assumes only locality (not even QM -- it is valid  
in classical physics also).


Locality, and identity preservation (or mono-universe, or  
counterfactual definiteness: all go away with Everett).



3. The Aspect et al., and subsequent, experiments demonstrate that  
the Bell inequalities are violated.


Yes, but only from the points of view of one branch. But when we look  
how the singlet state is handled in the MWI, the correlation are  
apparent, but the results obtained by space-separated person does not  
need to be correlated, in some absolute sense, they need to be  
correlated with anyone interacting with both of them later, so that in  
all branches, it will look like if there has been an action at a  
distance, but all influence and information flows, and splitting, go  
at a speed lower than light.





It seems to follow with the force of simple logic that:

4. Experiment shows that QM is non-local, even in MWI.

Bruno appears to reject this conclusion. I conclude that Bruno's  
position is incoherent.


I will again ask you to tell me what is wrong with Michael Clive Price  
explanation ... except that the web page is not available.


I am not alone skeptical about inferring that the violation of the  
Bell inequalities shows action at a distance. What is wrong in Deutsch  
and Hayden? What is wrong in Rubin (Rubin, M.A. Found Phys Lett (2001)  
14: 301. doi:10.1023/A:1012357515678), or in Maudlin's book?


It seems obvious that both Bell and EPR assumes the identity of the  
observers, who prepare the singlet state and measure the correlation,  
but this is simply made false in the MWI.


I have to go.

Bruno





Bruce

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 05 Jun 2017, at 04:19, Bruce Kellett wrote:


On 4/06/2017 10:05 pm, Bruno Marchal wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:

In QM, with or without collapse, decoherence and the transition  
from the pure state to a mixture gives a definite measurement  
result.


In particular branches only. When looking at the whole wave  
including the observers, decoherence explain why it *looks*, to all  
observers in the different branches, that mixed states have been  
obtained, but that is not the case in the global description.


The transition to the mixed state is essential for one to get a  
definite experimental result.


I agree. But this needs to happen from the subject point of view only.  
If Alice looks at a dead+alive cat, she split/differentiate in seeing  
a cat alive or a cat dead, although in the big picture she put herself  
in the superposition seeing the cat alive = seeing the cat dead. OK?





Physicists realized a long time ago that the pure unreduced state of  
the MWI does not work. The difficulty is known as the 'basis  
problem'. If you retain the full superposition of the pure state,  
there is no preferred basis, and expanding this superposition in  
terms of different bases gives different -- usually nonsensical --  
physical results. It is only when you reduce to a mixed state that  
the basis is fixed, and results are definite.


This will happen in the relevant basis, and *that* happens whatever  
base is chosen for the universal wave.





This does not mean, as you appear to think, that you have lost the  
other branches. All the branches of the MWI are still present,  
except that now there is a different definite measurement result in  
each branch.


That is exactly what I meant.






Without collapse, different branches get different results, but  
once obtained, these results are fixed, and are not affected by  
whether Alice and Bob exchange information or not.


I agree. That is used in the fact that in EPR like situation, when  
Alice and Bob are space-time separated, what we have is "only" an  
infinity of Alices and Bobs,


This is wrong. There is no "infinity of Alices and Bobs".


?

There is one Alice-Bob pair for each possible spin direction, or  
polarizer angle. Contrary to what the notation of the singlet state  
suggest, there is no preferential polarizer angle.







all with their spin correlated, and when Alice makes her  
measurement, at any angle, she will know Bob's possible result,


Bobs possible results, as far as Alice knows, is 50/50 for '+' or '-'.

without needing any action at a distance. She just localize  
herself, and her corresponding Bob, in which branch they belong.


That is not correct. You keep saying it, but you offer no proof or  
mechanism whereby such a thing could happen.


I did, and Saibal Mitra have point on the same reasoning done, many  
times. I have referred to Steven Price, also.






There is no influence at a distance, although we would need it to  
talk of token unique Alice and Bob in case there would be only one  
universe.


That is a total misunderstanding as well. All branches might exist  
(two for Alice in this case, one where she got '+' and one where she  
got '-'), but we need consider only one typical branch to get the  
general result -- that is how things are done in physics when you  
have superpositions.


When they are space separated, and make both measurement in non  
perpendicular angle, I don't see how we could talk of any typical  
branch. In that case thay might find any random result, even  
uncorrelated one. But they will never be aware of this, as they will  
compare the results later only with the part of the multiverse on  
which their respective (uncorrelated a priori) outcome will contagiate  
to the Alice (resp. Bob) they will be able to communicate with.


So, it is only because you maintain the identity of Alice and Bob  
throughout the experience, that you can interpret the violation of the  
inequality as an influence at a distance. That does not make sense  
once you keep track of the "slow" spreading of the superposition on  
their respective environment, in all relevant branches we started with.


Bruno








But there is non-locality -- non-local influence -- in all  
interpretations since it is inherent in the quantum formalism.


I don't see any non-locality in the MWI. EPR, Bell, assumes always  
one Alice and Bob, and as Everett shows, decoherence explains the  
manitenance of coherent first person plural description, and the  
absence of collapse prevent any non-local influence.


That is not the case either. Bell does not assume a necessary  
collapse. Bell's theorem is a mathematical theorem, it is true  
whatever interpretation of QM you adopt. You seem to be suggesting  
(and you are more explicit in this suggestion elsewhere) that Bell's  
theorem is invalid for MWI.


1. That is not true -- Bell's theorem is valid in all interpretations.
2. Even i

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 5/06/2017 12:19 pm, Bruce Kellett wrote:

On 4/06/2017 10:05 pm, Bruno Marchal wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:


Your claim appears to be that Bell's theorem is not valid in MWI.


Bell's theorem is valid. His inequality does not even assume QM, but 
just locality.


I agree, but that is not what you were implying above. It seems that 
now you agree that the Bell inequalities assume only locality. But 
these inequalities are violated by experiment. That can only mean that 
the assumption of locality was wrong -- whatever interpretation of QM 
you adopt.


I think that this important part of recent exchanges might have got lost 
in the welter of to-and-fro.


Bruno accepts:

1. Bell's theorem (and the associated inequalities) are valid in MWI.
2. Bell's theorem assumes only locality (not even QM -- it is valid in 
classical physics also).
3. The Aspect et al., and subsequent, experiments demonstrate that the 
Bell inequalities are violated.


It seems to follow with the force of simple logic that:

4. Experiment shows that QM is non-local, even in MWI.

Bruno appears to reject this conclusion. I conclude that Bruno's 
position is incoherent.


Bruce

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 4/06/2017 10:05 pm, Bruno Marchal wrote:

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:

In QM, with or without collapse, decoherence and the transition from 
the pure state to a mixture gives a definite measurement result.


In particular branches only. When looking at the whole wave including 
the observers, decoherence explain why it *looks*, to all observers in 
the different branches, that mixed states have been obtained, but that 
is not the case in the global description.


The transition to the mixed state is essential for one to get a definite 
experimental result. Physicists realized a long time ago that the pure 
unreduced state of the MWI does not work. The difficulty is known as the 
'basis problem'. If you retain the full superposition of the pure state, 
there is no preferred basis, and expanding this superposition in terms 
of different bases gives different -- usually nonsensical -- physical 
results. It is only when you reduce to a mixed state that the basis is 
fixed, and results are definite. This does not mean, as you appear to 
think, that you have lost the other branches. All the branches of the 
MWI are still present, except that now there is a different definite 
measurement result in each branch.


Without collapse, different branches get different results, but once 
obtained, these results are fixed, and are not affected by whether 
Alice and Bob exchange information or not.


I agree. That is used in the fact that in EPR like situation, when 
Alice and Bob are space-time separated, what we have is "only" an 
infinity of Alices and Bobs,


This is wrong. There is no "infinity of Alices and Bobs".

all with their spin correlated, and when Alice makes her measurement, 
at any angle, she will know Bob's possible result,


Bobs possible results, as far as Alice knows, is 50/50 for '+' or '-'.

without needing any action at a distance. She just localize herself, 
and her corresponding Bob, in which branch they belong.


That is not correct. You keep saying it, but you offer no proof or 
mechanism whereby such a thing could happen.


There is no influence at a distance, although we would need it to talk 
of token unique Alice and Bob in case there would be only one universe.


That is a total misunderstanding as well. All branches might exist (two 
for Alice in this case, one where she got '+' and one where she got 
'-'), but we need consider only one typical branch to get the general 
result -- that is how things are done in physics when you have 
superpositions.





But there is non-locality -- non-local influence -- in all 
interpretations since it is inherent in the quantum formalism.


I don't see any non-locality in the MWI. EPR, Bell, assumes always one 
Alice and Bob, and as Everett shows, decoherence explains the 
manitenance of coherent first person plural description, and the 
absence of collapse prevent any non-local influence.


That is not the case either. Bell does not assume a necessary collapse. 
Bell's theorem is a mathematical theorem, it is true whatever 
interpretation of QM you adopt. You seem to be suggesting (and you are 
more explicit in this suggestion elsewhere) that Bell's theorem is 
invalid for MWI.


1. That is not true -- Bell's theorem is valid in all interpretations.
2. Even if you did find an error in Bell's theorem, all that that would 
get you is the possibility of a local hidden-variable account of the 
correlations. If you think such a local hidden variable account is 
possible, then give it - in full mathematical detail - and we might 
begin to think that you know what you are talking about.





You cannot get away by reversing the onus of proof. Bell's theorem is 
independent of whether or not a collapse is assumed,


To interpret the experimental violation, you need to identify the 
Alice and Bob you talk about. But EPR and Bell talk of Alice and Bob 
like if they were in a definite universe all along the experience, 
when that is never the case. They do assume implicitly one physical 
universe.


Not true. See above. Even if this were the case so that the theorem was 
not valid in MWI, that actually does not get you anywhere -- 
non-locality would still exist, except that now you could give a local 
hidden variable account. I see no sign that you are actually doing this.


so if you want to argue that MWI removes the non-locality proved by 
Bell, then the onus of proof is very much on you: you have to 
demonstrate how this can be possible.


It is a trivial consequence of the linear differential shroedinger 
equation. Or of the fact that the evolution is a rotation (unitary) in 
Hilbert space.


Rubbish. If you remain with the linear Schrödinger equation, you cannot 
get definite results for experiments. Once you have definite results, as 
you need to calculate correlations, the non-locality is evident.




You say that Bell's theorem relies on the unicity of outcomes. By 
this, I presume you mean that Bell assumes counterfactua

Re: A thought on MWI and its alternative(s)

[John Clark]

On Thu, Jun 1, 2017 at 8:19 AM, Bruno Marchal  wrote:

​> ​
>  I was juste arguing against John Clarks idea that the Bell's inequality
> violation introduce physical action at a distance, even with the MWI.


​That's ​not exactly correct, what I actually said was *at least* one of
the following 3 things must be untrue:

​1) Determinism
2) Locality
3) Realism

Einstein thought all 3 were true but he died 10 years before Bell's
inequality had even been discovered and 30 years before experiments had
shown it was violated. You can't have everything and I think Einstein would
have been least horrified if #1 was untrue and most horrified if #3 was.

John K Clark

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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 04 Jun 2017, at 08:52, Telmo Menezes wrote:


Sure, we can take the same drug and talk about our experiences, and

conclude that they were similar. And they probably were. But
ultimately, there is a language grounding problem. We have no way of
comparing qualia, private experience. I cannot even verify
experimentally that you are indeed conscious. I assume it
heuristically, that's all.


OK. Let me tell you how I think about it, heuristically at least,  
as you
say. From my first-personal perspective, 'you' - that is your body  
- can
only ever be said to be "conscious' in the brutely covariate sense.  
For that
matter, the same goes for my observation of my own body. As you  
say, there's
no conceivable objective test that could establish more than this.  
Nor - and
this is telling - would anything more than neurocognition, at least  
in
principle, be required to account for your, or my own, observable  
behaviour.


I agree.

I think we need to accept that this is indeed telling us something.  
But
what? In my view it's telling us to stop thinking of consciousness  
as being

'explained' exclusively with reference to its observable physical
correlates. IOW this is possibly a paradigm case of the distinction  
between

correlation and causation.


Yes, this is all I'm saying too!


The alternative - shorn of its uniquely a
posteriori relation with one's own consciousness - would be in  
effect simply
to accept that physical behaviour is its own 'explanation'. This is  
the
conclusion Brent urges on us and I can respect this position  
without being

content with it myself.


Right, I can also understand Brent's positions. One of the reasons why
I am not satisfied with such a position is that consciousness appears
to be unnecessary from an intelligence / Darwinian standpoint. It
appears that Darwinism + neuroscience/computer science can explain the
emergence of our behaviour in non-conscious zombies. It has been
argued that it could be a spandrel, a by-product of the evolutionary
process. I have no problem with that -- in fact I am betting this is
the case, because I doubt that a non-conscious human-level
intelligence is possible. But I still want to know why.

Every time a problem baffles us, and people suggest that: "look, it's
just a brute fact", I can't help but feel that this stance is very
akin to saying "the gods did it". One of the things I like about
Bruno's work is that I fell that he, at least, provides a theory on
why it looks so mysterious to us.

What also baffles me is why some people can't see the mystery. I don't
think this is the case with Brent though, I think he is a pragmatist
-- which is a perfectly reasonable thing to be.

To go beyond this, as for example Bruno is attempting to do with  
the comp

theory, requires an explanatory schema that somehow manages both to
transcend and encapsulate the explication of conscious phenomena in
exclusively reductive terms. And to strip this move of any sense of
arbitrariness or avoidance of the problem we also need to show that  
this is
a necessary consequence of situating those phenomena adequately  
within a
tractable theory of knowledge. Such a theory will then focus on  
explicating
a characteristic logic of consciousness in terms of what is  
perceptible or
not, what is doubtable or not, what is communicable or not, and so  
forth.
And of course a crucial component of this must be the relation of  
these
categories to the dynamics of the necessarily correlated 'physics  
of the

observable'.


Yes, this is something I would like to see Bruno talk about more: how
he hopes to derive physics from his theory.


By convincing courageous people to pursue the extraction of the  
quantum logics from the arithmetical "material hypostases". This  
means, notably, to optimize the theorem prover for G and G*, and the  
variants.
We need "only" an army of mathematicians working in a department of  
theology in some science academy ...


By UDA, the physical is given by, either Bp & p, or Bp & Dt, or Bp &  
Dt & p. (anything giving Bp -> Dp, so that we have a notion of bet).


Normally the first person plural one should be the one given by Bp & Dt.

p is for sigma_1 proposition, the "leaves" of the universal  
dovetailing, and B is for Gödel's beweisbar predicate, where all those  
nuances are enforced by incompleteness theorem for any machine betting  
on computationalism and trying to predict its consistent extension in  
arithmetic.


We do have the three quantum logics, and their corresponding  
quantization (the logic of []<>p, to "reverse" Goldblatt's translation  
of the modal logic into quantum logic) gives the quantum relations,  
from which it is hoped we get enough (we know we do get something  
complete, in some sense) to get either Gleason theorem, or a  
corresponding one.


The qualia should be given by S4Grz1 and X1* minus X1. But the quanta  
are sort of qualia, partially sharable and seems to appear in the  
three physics we get.

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 4 Jun 2017 1:05 p.m., "Bruno Marchal"  wrote:


On 02 Jun 2017, at 03:01, Bruce Kellett wrote:

On 1/06/2017 10:19 pm, Bruno Marchal wrote:
>
>> On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
>> On 1/06/2017 4:43 am, Bruno Marchal wrote:
>>
>>> On 31 May 2017, at 04:01, Bruce Kellett wrote:

> On 30/05/2017 9:35 pm, Bruno Marchal wrote:
>
>> On 30 May 2017, at 11:28, Telmo Menezes wrote:
>>
>> I get your point with decoherence.
>>> Again, I would say that it all depends on theories of mind. What does
>>> mind supervene on? Perhaps it is true that every single coupling with
>>> the environment prevents the current observer state to become
>>> compatible with other branches. But can we be sure? I feel that such
>>> certainties come from a strong belief in emergentism (which I cannot
>>> disprove, but find problematic).
>>>
>>
>> It is impossible to recohere the past, FAPP.
>>
>> But only FAPP. To make the blue T-rex interfereing with the
>> red-T-rex, we must erase the trace of particle interaction between the
>> T-rex in its whole light-cone, and this without forgetting the particles
>> "swallowed" by the black-holes, etc. It is just completely impossible, 
>> but
>> to derive from that the unicity of the past, is, it seems to me (and you 
>> if
>> I understood well) is invalid.
>>
>
> I think the recoherence of paths that have completely decohered is
> more than just FAPP impossible, I think it is impossible in principle. One
> major problem with recoherence in general is that information leaks from
> the paths at the speed of light (as well as less slowly for other
> interactions). Since this vital information goes out along the light cone,
> it can never be recaptured and returned to the original interaction.
>

 In QM + special relativity OK. (note that to me QM + special relativity
 => no collapse (and even the Many dreams, but we have agreed to disagree on
 this if I remember well).

>>>
>>> Reasoning in QM without SR is not very profitable. Besides, QM + SR does
>>> not particularly imply MWI -- it is perfectly possible to have a consistent
>>> collapse model of QM+SR. I know you don't agree because of the non-locality
>>> implied by EPR, but this non-locality is not removed in MWI, regardless of
>>> what you might say.
>>>
>>
>> I don't see it, and the mast time we discuss this, we conclude on some
>> vocabulary problem. When there is no collapse, measurement tells to people
>> light separated in which branch theiy belongs, but to exploits that
>> information, they need to come into contact.
>>
>
> Last time we discussed this, no resolution was achieved.
>

That is not what I remembered, but I will not insist.





In QM, with or without collapse, decoherence and the transition from the
> pure state to a mixture gives a definite measurement result.
>

In particular branches only. When looking at the whole wave including the
observers, decoherence explain why it *looks*, to all observers in the
different branches, that mixed states have been obtained, but that is not
the case in the global description.





Without collapse, different branches get different results, but once
> obtained, these results are fixed, and are not affected by whether Alice
> and Bob exchange information or not.
>

I agree. That is used in the fact that in EPR like situation, when Alice
and Bob are space-time separated, what we have is "only" an infinity of
Alices and Bobs, all with their spin correlated, and when Alice makes her
measurement, at any angle, she will know Bob's possible result, without
needing any action at a distance. She just localize herself, and her
corresponding Bob, in which branch they belong. There is no influence at a
distance, although we would need it to talk of token unique Alice and Bob
in case there would be only one universe.





> Consequently, indispensable phase information is lost *in principle*, so
> the recoherence is, in general, impossible.
>

 OK. (I was reasoning in naive classical QM)

 Of course, with carefully constructed systems, where the loss of
> information along the light cone is prevented, recoherence is possible in
> special circumstances, but not in general.
>
> From this, the uniqueness of the past of any decoherent history is
> assured. So deriving the unicity (if I understand this use of the word) is
> by no means invalid -- it is proved.
>

 In QM + SR. OK.

 Even if one encounters one of those rare situations in which
> recoherence is achieved, that still does not invalidate the uniqueness of
> the past history -- recoherence, if it occurs, simply means that no new
> branches are formed at that point, so the decoherent history remains 
> unique.
>

 OK. That might suggest that we identify our indistinguishible past in

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 02 Jun 2017, at 04:06, Bruce Kellett wrote:


 (answered in my previous post).

In quantum mechanics, this change is brought about by the unitary  
processes of decoherence,


As Everett explains well, and suggest already this makes any  
influence at a distance only apparent, but never real. Einstein can  
sleep well.




and the non-unitary trace over the environmental degrees of freedom.


Which reflects only, in the MWI, the contagion of the superposition  
to the environment.



This is an essential difference between classical and quantum  
physics, and the necessity for this non-unitary reduction of the  
pure state to a mixture is ultimately why MWI is actually no  
better at explaining quantum measurement than are the collapse  
models.


Only if you interpret the decoherence as a physical phenomenon, but  
then we get non unitary evolution in Nature, and -quantum mechanics- 
without collapse is false.


Are you suggesting that decoherence is *not* a physical phenomenon?


I am saying that the first person seeing mixed states is a first  
person valid seeing from its "personal branch" perspective, but there  
is no definite outcome in the third person view we can have on the  
wave or the formalism.




Decoherence and the pure-to-mixed transition do indeed say that MWI  
is strictly false -- you need non-unitary additions.


?

Only the collapse, if real, needs to falsify the unitarity of the  
evolution.







The question is, what determined (from the 3p view) that the  
universe followed that particular path and not any of the others?


Why do you reject out of hand that the universe might be  
probabilistic?  It is possible 'nothing' determined which path  
from the possibilities was actually followed. All that is known  
are the probabilities for each path. We do not know that the  
other paths are followed, either 1p or 3p.


In QM, we do have evidences that many path are taken all  
together. if only the two slits.


That is not really a relevant comment. Quantum mechanics is  
characterized by the presence of superpositions -- that is what  
makes the theory work, and why it is so different from classical  
physics. Superpositions generally represent pure states, and these  
must be reduced to mixed states by the measurement process.


Without collapse, that never happens.


So your non-collapse theory is immediately falsified by every  
quantum experiment ever performed.



It is falsified only if you take a definite outcome as being absolute  
and not branch relative.


Bruno



http://iridia.ulb.ac.be/~marchal/



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Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 02 Jun 2017, at 03:01, Bruce Kellett wrote:


On 1/06/2017 10:19 pm, Bruno Marchal wrote:

On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:

On 31 May 2017, at 04:01, Bruce Kellett wrote:

On 30/05/2017 9:35 pm, Bruno Marchal wrote:

On 30 May 2017, at 11:28, Telmo Menezes wrote:


I get your point with decoherence.
Again, I would say that it all depends on theories of mind.  
What does
mind supervene on? Perhaps it is true that every single  
coupling with

the environment prevents the current observer state to become
compatible with other branches. But can we be sure? I feel  
that such
certainties come from a strong belief in emergentism (which I  
cannot

disprove, but find problematic).


It is impossible to recohere the past, FAPP.

But only FAPP. To make the blue T-rex interfereing with the red- 
T-rex, we must erase the trace of particle interaction between  
the T-rex in its whole light-cone, and this without forgetting  
the particles "swallowed" by the black-holes, etc. It is just  
completely impossible, but to derive from that the unicity of  
the past, is, it seems to me (and you if I understood well) is  
invalid.


I think the recoherence of paths that have completely decohered  
is more than just FAPP impossible, I think it is impossible in  
principle. One major problem with recoherence in general is that  
information leaks from the paths at the speed of light (as well  
as less slowly for other interactions). Since this vital  
information goes out along the light cone, it can never be  
recaptured and returned to the original interaction.


In QM + special relativity OK. (note that to me QM + special  
relativity => no collapse (and even the Many dreams, but we have  
agreed to disagree on this if I remember well).


Reasoning in QM without SR is not very profitable. Besides, QM +  
SR does not particularly imply MWI -- it is perfectly possible to  
have a consistent collapse model of QM+SR. I know you don't agree  
because of the non-locality implied by EPR, but this non-locality  
is not removed in MWI, regardless of what you might say.


I don't see it, and the mast time we discuss this, we conclude on  
some vocabulary problem. When there is no collapse, measurement  
tells to people light separated in which branch theiy belongs, but  
to exploits that information, they need to come into contact.


Last time we discussed this, no resolution was achieved.


That is not what I remembered, but I will not insist.




In QM, with or without collapse, decoherence and the transition from  
the pure state to a mixture gives a definite measurement result.


In particular branches only. When looking at the whole wave including  
the observers, decoherence explain why it *looks*, to all observers in  
the different branches, that mixed states have been obtained, but that  
is not the case in the global description.





Without collapse, different branches get different results, but once  
obtained, these results are fixed, and are not affected by whether  
Alice and Bob exchange information or not.


I agree. That is used in the fact that in EPR like situation, when  
Alice and Bob are space-time separated, what we have is "only" an  
infinity of Alices and Bobs, all with their spin correlated, and when  
Alice makes her measurement, at any angle, she will know Bob's  
possible result, without needing any action at a distance. She just  
localize herself, and her corresponding Bob, in which branch they  
belong. There is no influence at a distance, although we would need it  
to talk of token unique Alice and Bob in case there would be only one  
universe.






Consequently, indispensable phase information is lost *in  
principle*, so the recoherence is, in general, impossible.


OK. (I was reasoning in naive classical QM)

Of course, with carefully constructed systems, where the loss of  
information along the light cone is prevented, recoherence is  
possible in special circumstances, but not in general.


From this, the uniqueness of the past of any decoherent history  
is assured. So deriving the unicity (if I understand this use of  
the word) is by no means invalid -- it is proved.


In QM + SR. OK.

Even if one encounters one of those rare situations in which  
recoherence is achieved, that still does not invalidate the  
uniqueness of the past history -- recoherence, if it occurs,  
simply means that no new branches are formed at that point, so  
the decoherent history remains unique.


OK. That might suggest that we identify our indistinguishible  
past in arithmetic, if we assume mechanism. I use the Y = II  
principle, or the "quantum" linearity of the tensor product "@":  
we have that  a @ (b + c) = (a @ b) + (a @ c).


That makes sense.


Linearity is the heart of QM. It is linearity that allows  
superpositions, and leads to all the "quantum weirdness".


I agree. Both "linearities" (the quantum evolution, and the tensor  
product

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 4 Jun 2017 7:53 a.m., "Telmo Menezes"  wrote:

> Sure, we can take the same drug and talk about our experiences, and
>
> conclude that they were similar. And they probably were. But
> ultimately, there is a language grounding problem. We have no way of
> comparing qualia, private experience. I cannot even verify
> experimentally that you are indeed conscious. I assume it
> heuristically, that's all.
>
>
> OK. Let me tell you how I think about it, heuristically at least, as you
> say. From my first-personal perspective, 'you' - that is your body - can
> only ever be said to be "conscious' in the brutely covariate sense. For
that
> matter, the same goes for my observation of my own body. As you say,
there's
> no conceivable objective test that could establish more than this. Nor -
and
> this is telling - would anything more than neurocognition, at least in
> principle, be required to account for your, or my own, observable
behaviour.

I agree.

> I think we need to accept that this is indeed telling us something. But
> what? In my view it's telling us to stop thinking of consciousness as
being
> 'explained' exclusively with reference to its observable physical
> correlates. IOW this is possibly a paradigm case of the distinction
between
> correlation and causation.

Yes, this is all I'm saying too!

> The alternative - shorn of its uniquely a
> posteriori relation with one's own consciousness - would be in effect
simply
> to accept that physical behaviour is its own 'explanation'. This is the
> conclusion Brent urges on us and I can respect this position without being
> content with it myself.

Right, I can also understand Brent's positions. One of the reasons why
I am not satisfied with such a position is that consciousness appears
to be unnecessary from an intelligence / Darwinian standpoint. It
appears that Darwinism + neuroscience/computer science can explain the
emergence of our behaviour in non-conscious zombies. It has been
argued that it could be a spandrel, a by-product of the evolutionary
process. I have no problem with that -- in fact I am betting this is
the case, because I doubt that a non-conscious human-level
intelligence is possible. But I still want to know why.

Every time a problem baffles us, and people suggest that: "look, it's
just a brute fact", I can't help but feel that this stance is very
akin to saying "the gods did it". One of the things I like about
Bruno's work is that I fell that he, at least, provides a theory on
why it looks so mysterious to us.

What also baffles me is why some people can't see the mystery. I don't
think this is the case with Brent though, I think he is a pragmatist
-- which is a perfectly reasonable thing to be.

> To go beyond this, as for example Bruno is attempting to do with the comp
> theory, requires an explanatory schema that somehow manages both to
> transcend and encapsulate the explication of conscious phenomena in
> exclusively reductive terms. And to strip this move of any sense of
> arbitrariness or avoidance of the problem we also need to show that this
is
> a necessary consequence of situating those phenomena adequately within a
> tractable theory of knowledge. Such a theory will then focus on
explicating
> a characteristic logic of consciousness in terms of what is perceptible or
> not, what is doubtable or not, what is communicable or not, and so forth.
> And of course a crucial component of this must be the relation of these
> categories to the dynamics of the necessarily correlated 'physics of the
> observable'.

Yes, this is something I would like to see Bruno talk about more: how
he hopes to derive physics from his theory.

> I have no problem with theories of mind,
> but I am not sure that we can expect them to be validated or refuted
> in the some way that other theories can be.
>
>
> That's right. Not in the same way, but perhaps nonetheless, in principle
and
> with justification, to the extent that it can be said to be explained at
> all.

Yes. In the end, some weirdness is to be expected. After all, the
attempt to understand consciousness amounts to something creating
theory on itself. After all, we only have the first-person view. The
third-person view of reality is an abstraction. Independently of one's
position on MWI, comp, physicalism, idealism, etc, one only knows
reality in the 1p. Trying to understand consciousness is trying to
understand 1p from the 1p. If logic has taught me anything, it's that
once you apply something to itself, strange things happen...

>
>>> Indirect measures of consciousness entail hidden
>>> assumptions, and it becomes easy to beg the question.
>>
>>
>> Which particular question did you have in mind?
>
> For example: does consciousness in humans supervene only on brain
> activity?
>
>
> Well, in the terms I've set out: Yes if you you mean the indispensable
> necessity of covariance with the observable physics, which is to say the
> spectrum of perceptible externality and its theoretical ontology. 

Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

> Sure, we can take the same drug and talk about our experiences, and
>
> conclude that they were similar. And they probably were. But
> ultimately, there is a language grounding problem. We have no way of
> comparing qualia, private experience. I cannot even verify
> experimentally that you are indeed conscious. I assume it
> heuristically, that's all.
>
>
> OK. Let me tell you how I think about it, heuristically at least, as you
> say. From my first-personal perspective, 'you' - that is your body - can
> only ever be said to be "conscious' in the brutely covariate sense. For that
> matter, the same goes for my observation of my own body. As you say, there's
> no conceivable objective test that could establish more than this. Nor - and
> this is telling - would anything more than neurocognition, at least in
> principle, be required to account for your, or my own, observable behaviour.

I agree.

> I think we need to accept that this is indeed telling us something. But
> what? In my view it's telling us to stop thinking of consciousness as being
> 'explained' exclusively with reference to its observable physical
> correlates. IOW this is possibly a paradigm case of the distinction between
> correlation and causation.

Yes, this is all I'm saying too!

> The alternative - shorn of its uniquely a
> posteriori relation with one's own consciousness - would be in effect simply
> to accept that physical behaviour is its own 'explanation'. This is the
> conclusion Brent urges on us and I can respect this position without being
> content with it myself.

Right, I can also understand Brent's positions. One of the reasons why
I am not satisfied with such a position is that consciousness appears
to be unnecessary from an intelligence / Darwinian standpoint. It
appears that Darwinism + neuroscience/computer science can explain the
emergence of our behaviour in non-conscious zombies. It has been
argued that it could be a spandrel, a by-product of the evolutionary
process. I have no problem with that -- in fact I am betting this is
the case, because I doubt that a non-conscious human-level
intelligence is possible. But I still want to know why.

Every time a problem baffles us, and people suggest that: "look, it's
just a brute fact", I can't help but feel that this stance is very
akin to saying "the gods did it". One of the things I like about
Bruno's work is that I fell that he, at least, provides a theory on
why it looks so mysterious to us.

What also baffles me is why some people can't see the mystery. I don't
think this is the case with Brent though, I think he is a pragmatist
-- which is a perfectly reasonable thing to be.

> To go beyond this, as for example Bruno is attempting to do with the comp
> theory, requires an explanatory schema that somehow manages both to
> transcend and encapsulate the explication of conscious phenomena in
> exclusively reductive terms. And to strip this move of any sense of
> arbitrariness or avoidance of the problem we also need to show that this is
> a necessary consequence of situating those phenomena adequately within a
> tractable theory of knowledge. Such a theory will then focus on explicating
> a characteristic logic of consciousness in terms of what is perceptible or
> not, what is doubtable or not, what is communicable or not, and so forth.
> And of course a crucial component of this must be the relation of these
> categories to the dynamics of the necessarily correlated 'physics of the
> observable'.

Yes, this is something I would like to see Bruno talk about more: how
he hopes to derive physics from his theory.

> I have no problem with theories of mind,
> but I am not sure that we can expect them to be validated or refuted
> in the some way that other theories can be.
>
>
> That's right. Not in the same way, but perhaps nonetheless, in principle and
> with justification, to the extent that it can be said to be explained at
> all.

Yes. In the end, some weirdness is to be expected. After all, the
attempt to understand consciousness amounts to something creating
theory on itself. After all, we only have the first-person view. The
third-person view of reality is an abstraction. Independently of one's
position on MWI, comp, physicalism, idealism, etc, one only knows
reality in the 1p. Trying to understand consciousness is trying to
understand 1p from the 1p. If logic has taught me anything, it's that
once you apply something to itself, strange things happen...

>
>>> Indirect measures of consciousness entail hidden
>>> assumptions, and it becomes easy to beg the question.
>>
>>
>> Which particular question did you have in mind?
>
> For example: does consciousness in humans supervene only on brain
> activity?
>
>
> Well, in the terms I've set out: Yes if you you mean the indispensable
> necessity of covariance with the observable physics, which is to say the
> spectrum of perceptible externality and its theoretical ontology. No if you
> mean an explanatory theory of knowledg

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 3/06/2017 4:07 pm, smitra wrote:

On 03-06-2017 05:42, Bruce Kellett wrote:

On 3/06/2017 11:38 am, smitra wrote:

On 03-06-2017 02:10, Bruce Kellett wrote:

On 3/06/2017 9:16 am, smitra wrote:

In a single universe theory, this implies non-locality, because of 
the absence of local hidden variables. If local  hidden variable 
were to exist then you could say that Alice and Bob where to find 
whatever they found anyway only due to their local interactions 
with the spins and polarizers. But with that ruled out, whatever 
Alice will find is information that just popped into existence 
when Bob made his measurement.


What is ruled out by Bell's theorem is that local hidden variables can
account for all possible correlations between the observations, Bell's
theorem does not rule out the possibility of a local hidden variable
explanation in special cases, like that of polarizers set at the same
angle.


Either  there exists a local hidden variable theory from which QM 
can be derived or such a theory doesn't exist. If we assume that a 
local hidden variable theory underlies QM, then we find that 
regardless of the details, it cannot reproduce QM in certain cases. 
Bell inequalities can be derived for such theories that QM violates. 
Then, with QM confirmed and in particular the violations of the Bell 
inequalities conformed, we can then discard any local hidden 
variables theory.


This means that even in cases that do not involve violations of Bell 
inequalities,  we can still say that there are no local hidden 
variables that can explain the results in those experiments, because 
we've verified that there is no hidden variable theory that can 
reproduce QM.


Reproduce all QM results. It does not rule out cases where local
hidden variable, or common cause, explanations are possible.

Then it suffices to consider a simple case of entanglement between 
two spins where in a single universe interpretation there is 
non-local behavior, e.g. Alice and Bob measuring the z-components of 
a system of two spin 1/2 particles in the singlet state. You may 
consider more complex cases where Alice randomly chooses another 
direction, but I remember from a previous discussion that this led 
to a disagreement about how to treat the source of this randomness.


Not that I remember. There might have been disagreement about how the
orientation of one polarizer became known at the other polarizer, but
randmoness was never an issue.

Ultimately all randomness has a quantum mechanical origin as pointed 
out in this article:


https://arxiv.org/abs/1212.0953

There simply exists no known way to get to purely classical randomness.

In the case where both polarizers have the same setting, the fact 
that Bob knows what Alice will find poses a problem for locality 
because local hidden variables have been ruled out.


No it doesn't. There is a simple common cause explanation available
for this case.


Which doesn't eliminate non-local effects, see EPR.


 So, what Alice will find is random, new information will appear at 
her place after she measures the spin that didn't previously exist 
locally. But the fact that Bob could predict her result means that 
this information did exist at Bob's place. This demonstrates the 
non-locality aspect of single universe theories.


No, it simply demonstrates that when there is a common cause
explanation, there is no problem. Remember Bertlmann's socks.


No, see EPR argument.


Then in the MWI, Alice is identical in the two branches, so her 
measurement result is not predetermined as she is not yet located in 
either of Bob's branches. Her measurement result will do that.


Not so. When the polarizers are aligned, Bob's measurement has a
common cause with Alice's, so the agreement between results is
determined from the start.



Agreement  via common cause does not eliminate non-locality problem in 
single universe theories, as EPR have shown.


The common cause I was referring to was the possibility that Alice 
getting '+' and Bob getting '-' might have been because the electrons 
left the common source in that state (not singlet). Not a good 
explanation, I admit, but akin to Bertlmann's socks.



If we change the set-up by letting Alice choose different setting of 
her polarizer to bring in the additional baggage of having to rule 
out hidden variables within the same experiment so that non-locality 
arguments have to be re-argued based on that, then that's not going 
to add anything but confusion.


It might confuse you, but until you can do this you have not achieved
a local explanation of the general case in which the polarizers are at
arbitrary angles to each other.

It seems that you are making valiant attempts to avoid the case where
the shit hits the fan. Good luck with that, but I am not fooled.

Bruce


It's totally irrelevant, but I'll write out the GHZ state case with 3 
entangled spins and 3 observers that measure the x and y components of 
the spins to demonstrate step by ste

Re: A thought on MWI and its alternative(s)

[smitra]

On 03-06-2017 05:42, Bruce Kellett wrote:

On 3/06/2017 11:38 am, smitra wrote:

On 03-06-2017 02:10, Bruce Kellett wrote:

On 3/06/2017 9:16 am, smitra wrote:

In a single universe theory, this implies non-locality, because of 
the absence of local hidden variables. If local  hidden variable 
were to exist then you could say that Alice and Bob where to find 
whatever they found anyway only due to their local interactions with 
the spins and polarizers. But with that ruled out, whatever Alice 
will find is information that just popped into existence when Bob 
made his measurement.


What is ruled out by Bell's theorem is that local hidden variables 
can
account for all possible correlations between the observations, 
Bell's

theorem does not rule out the possibility of a local hidden variable
explanation in special cases, like that of polarizers set at the same
angle.


Either  there exists a local hidden variable theory from which QM can 
be derived or such a theory doesn't exist. If we assume that a local 
hidden variable theory underlies QM, then we find that regardless of 
the details, it cannot reproduce QM in certain cases. Bell 
inequalities can be derived for such theories that QM violates. Then, 
with QM confirmed and in particular the violations of the Bell 
inequalities conformed, we can then discard any local hidden variables 
theory.


This means that even in cases that do not involve violations of Bell 
inequalities,  we can still say that there are no local hidden 
variables that can explain the results in those experiments, because 
we've verified that there is no hidden variable theory that can 
reproduce QM.


Reproduce all QM results. It does not rule out cases where local
hidden variable, or common cause, explanations are possible.

Then it suffices to consider a simple case of entanglement between two 
spins where in a single universe interpretation there is non-local 
behavior, e.g. Alice and Bob measuring the z-components of a system of 
two spin 1/2 particles in the singlet state. You may consider more 
complex cases where Alice randomly chooses another direction, but I 
remember from a previous discussion that this led to a disagreement 
about how to treat the source of this randomness.


Not that I remember. There might have been disagreement about how the
orientation of one polarizer became known at the other polarizer, but
randmoness was never an issue.

Ultimately all randomness has a quantum mechanical origin as pointed 
out in this article:


https://arxiv.org/abs/1212.0953

There simply exists no known way to get to purely classical 
randomness.


In the case where both polarizers have the same setting, the fact that 
Bob knows what Alice will find poses a problem for locality because 
local hidden variables have been ruled out.


No it doesn't. There is a simple common cause explanation available
for this case.


Which doesn't eliminate non-local effects, see EPR.


 So, what Alice will find is random, new information will appear at 
her place after she measures the spin that didn't previously exist 
locally. But the fact that Bob could predict her result means that 
this information did exist at Bob's place. This demonstrates the 
non-locality aspect of single universe theories.


No, it simply demonstrates that when there is a common cause
explanation, there is no problem. Remember Bertlmann's socks.


No, see EPR argument.


Then in the MWI, Alice is identical in the two branches, so her 
measurement result is not predetermined as she is not yet located in 
either of Bob's branches. Her measurement result will do that.


Not so. When the polarizers are aligned, Bob's measurement has a
common cause with Alice's, so the agreement between results is
determined from the start.



Agreement  via common cause does not eliminate non-locality problem in 
single universe theories, as EPR have shown.


If we change the set-up by letting Alice choose different setting of 
her polarizer to bring in the additional baggage of having to rule out 
hidden variables within the same experiment so that non-locality 
arguments have to be re-argued based on that, then that's not going to 
add anything but confusion.


It might confuse you, but until you can do this you have not achieved
a local explanation of the general case in which the polarizers are at
arbitrary angles to each other.

It seems that you are making valiant attempts to avoid the case where
the shit hits the fan. Good luck with that, but I am not fooled.

Bruce


It's totally irrelevant, but I'll write out the GHZ state case with 3 
entangled spins and 3 observers that measure the x and y components of 
the spins to demonstrate step by step that there is no problem in the 
MWI, while in the CI there is a non-locality problem later when I have 
time.


But in general, the EPR thought experiment  proves you wrong, the common 
cause there does not save you from non-local effects in single universe 
collapse theories.  Then Bell

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 3/06/2017 11:38 am, smitra wrote:

On 03-06-2017 02:10, Bruce Kellett wrote:

On 3/06/2017 9:16 am, smitra wrote:

In a single universe theory, this implies non-locality, because of 
the absence of local hidden variables. If local  hidden variable 
were to exist then you could say that Alice and Bob where to find 
whatever they found anyway only due to their local interactions with 
the spins and polarizers. But with that ruled out, whatever Alice 
will find is information that just popped into existence when Bob 
made his measurement.


What is ruled out by Bell's theorem is that local hidden variables can
account for all possible correlations between the observations, Bell's
theorem does not rule out the possibility of a local hidden variable
explanation in special cases, like that of polarizers set at the same
angle.


Either  there exists a local hidden variable theory from which QM can 
be derived or such a theory doesn't exist. If we assume that a local 
hidden variable theory underlies QM, then we find that regardless of 
the details, it cannot reproduce QM in certain cases. Bell 
inequalities can be derived for such theories that QM violates. Then, 
with QM confirmed and in particular the violations of the Bell 
inequalities conformed, we can then discard any local hidden variables 
theory.


This means that even in cases that do not involve violations of Bell 
inequalities,  we can still say that there are no local hidden 
variables that can explain the results in those experiments, because 
we've verified that there is no hidden variable theory that can 
reproduce QM.


Reproduce all QM results. It does not rule out cases where local hidden 
variable, or common cause, explanations are possible.


Then it suffices to consider a simple case of entanglement between two 
spins where in a single universe interpretation there is non-local 
behavior, e.g. Alice and Bob measuring the z-components of a system of 
two spin 1/2 particles in the singlet state. You may consider more 
complex cases where Alice randomly chooses another direction, but I 
remember from a previous discussion that this led to a disagreement 
about how to treat the source of this randomness.


Not that I remember. There might have been disagreement about how the 
orientation of one polarizer became known at the other polarizer, but 
randmoness was never an issue.


Ultimately all randomness has a quantum mechanical origin as pointed 
out in this article:


https://arxiv.org/abs/1212.0953

There simply exists no known way to get to purely classical randomness.

In the case where both polarizers have the same setting, the fact that 
Bob knows what Alice will find poses a problem for locality because 
local hidden variables have been ruled out.


No it doesn't. There is a simple common cause explanation available for 
this case.


 So, what Alice will find is random, new information will appear at 
her place after she measures the spin that didn't previously exist 
locally. But the fact that Bob could predict her result means that 
this information did exist at Bob's place. This demonstrates the 
non-locality aspect of single universe theories.


No, it simply demonstrates that when there is a common cause 
explanation, there is no problem. Remember Bertlmann's socks.


Then in the MWI, Alice is identical in the two branches, so her 
measurement result is not predetermined as she is not yet located in 
either of Bob's branches. Her measurement result will do that.


Not so. When the polarizers are aligned, Bob's measurement has a common 
cause with Alice's, so the agreement between results is determined from 
the start.


If we change the set-up by letting Alice choose different setting of 
her polarizer to bring in the additional baggage of having to rule out 
hidden variables within the same experiment so that non-locality 
arguments have to be re-argued based on that, then that's not going to 
add anything but confusion.


It might confuse you, but until you can do this you have not achieved a 
local explanation of the general case in which the polarizers are at 
arbitrary angles to each other.


It seems that you are making valiant attempts to avoid the case where 
the shit hits the fan. Good luck with that, but I am not fooled.


Bruce

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Re: A thought on MWI and its alternative(s)

[smitra]

On 03-06-2017 02:10, Bruce Kellett wrote:

On 3/06/2017 9:16 am, smitra wrote:

In a single universe theory, this implies non-locality, because of the 
absence of local hidden variables. If local  hidden variable were to 
exist then you could say that Alice and Bob where to find whatever 
they found anyway only due to their local interactions with the spins 
and polarizers. But with that ruled out, whatever Alice will find is 
information that just popped into existence when Bob made his 
measurement.


What is ruled out by Bell's theorem is that local hidden variables can
account for all possible correlations between the observations, Bell's
theorem does not rule out the possibility of a local hidden variable
explanation in special cases, like that of polarizers set at the same
angle.


Either  there exists a local hidden variable theory from which QM can be 
derived or such a theory doesn't exist. If we assume that a local hidden 
variable theory underlies QM, then we find that regardless of the 
details, it cannot reproduce QM in certain cases. Bell inequalities can 
be derived for such theories that QM violates. Then, with QM confirmed 
and in particular the violations of the Bell inequalities conformed, we 
can then discard any local hidden variables theory.


This means that even in cases that do not involve violations of Bell 
inequalities,  we can still say that there are no local hidden variables 
that can explain the results in those experiments, because we've 
verified that there is no hidden variable theory that can reproduce QM.


Then it suffices to consider a simple case of entanglement between two 
spins where in a single universe interpretation there is non-local 
behavior, e.g. Alice and Bob measuring the z-components of a system of 
two spin 1/2 particles in the singlet state. You may consider more 
complex cases where Alice randomly chooses another direction, but I 
remember from a previous discussion that this led to a disagreement 
about how to treat the source of this randomness.


Ultimately all randomness has a quantum mechanical origin as pointed out 
in this article:


https://arxiv.org/abs/1212.0953

There simply exists no known way to get to purely classical randomness.

In the case where both polarizers have the same setting, the fact that 
Bob knows what Alice will find poses a problem for locality because 
local hidden variables have been ruled out.   So, what Alice will find 
is random, new information will appear at her place after she measures 
the spin that didn't previously exist locally. But the fact that Bob 
could predict her result means that this information did exist at Bob's 
place. This demonstrates the non-locality aspect of single universe 
theories.


Then in the MWI, Alice is identical in the two branches, so her 
measurement result is not predetermined as she is not yet located in 
either of Bob's branches. Her measurement result will do that.


If we change the set-up by letting Alice choose different setting of her 
polarizer to bring in the additional baggage of having to rule out 
hidden variables within the same experiment so that non-locality 
arguments have to be re-argued based on that, then that's not going to 
add anything but confusion.


Saibal

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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 3/06/2017 9:16 am, smitra wrote:

On 02-06-2017 10:05, Bruce Kellett wrote:

On 2/06/2017 5:31 pm, smitra wrote:

On 02-06-2017 04:54, Bruce Kellett wrote:

On 2/06/2017 12:00 pm, smitra wrote:

On 02-06-2017 02:07, Bruce Kellett wrote:

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation 
of our belonging to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in 
Bell's

theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well 
as in

any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. 
There is no non-locality in some mysterious sense like there is 
in the CI where somehow there is a non-local effect but you 
don;t have information transfer. The mistake most people make 
when arguing that the MWI doesn't resolve the problem is that 
they can't get their head around the fact that even when Alice 
and Bob meet and Alice has not yet communicated everything 
that's necessary to Bob, that the Alice that Bob sees has yet to 
collapse in the branch corresponding to whatever she is going to 
say (Bob's consciousness is thus located in many different 
branches of Alice, even if the atoms in his body will be in 
different states due to decoherence).


I think that either you or someone else said something like this 
when

this was last discussed. I have a couple of points to make:

1. This is not quantum mechanics, or the many worlds 
interpretation of

QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.

2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be 
unrelated to
the decohered body. That conflicts with the overwhelming 
experimental

evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has 
decohered
having obtained a particular measurement result, all copies (if 
there

be such) of this consciousness are conscious of the same measurement
result. By the identity of indiscernibles, there is then only one 
body

and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.

Bruce




Suppose Alice and Bob are robots with classical processors, the 
states of each register can only be 0 and 1. Whatever Bob is 
conscious of must then be contained in the bitstring that 
specifies the state his processor is in. Decoherence has  no 
effect on that bitstring. Until that time that Bob asks Alice 
about her setting of her polarizer, Bob's consciousness is exactly 
the same across the different branches in which Alice gives a 
different answer,


False.


It's trivially true.


Bob's consciousness reflects the results he got. There are only four
branches: '++', '+-', '-+', and '--'. Bob's conscious state is
different for the two Alice '+' branches, and also different for the
two Alice '-' branches. So it is not invariant across Alice's
branches.


What  matters for the MWI discussion is simply that after Bob has made 
his measurement and he gets located in a branch corresponding to 
whatever he has measured, that whatever Alice does is not going to 
further localize Bob in a narrower set of branches due to decoherence 
caused by Alice's measurements.


Yes, in the case under discussion, there are only two branches for Bob 
(and two for Alice).


Here you then do need to extract Bob's consciousness from Bob's exact 
physical state.


We are doing quantum mechanics here, not a theory of consciousness. So 
the discussion must be restricted to the formalism of QM. Introducing 
Bob's conscious state is an obfuscation, because that does not appear in 
the equations -- only his physical state is relevant to QM.


It's only when Alice communicates the details that Bob's consciousness 
get's located in Alice's branches.


How? By magic?


despite rapid decoherence.

Real human beings can be expected to fit well within this model. 
It is known that there typically is a lot of information present 
in the unconscious mind that we're not aware of. So, your 
consciousness could be identical across many branches even if your 
brain had split and the unconscious mind is already diverging. 
Take e.g. experiments where you are making a random choice and on 
the basis on functional MRI scans the experimenters are able to 
predict your choice before you have even made up your mind.


So, this is same good old QM in the MWI where an observer's 
consciousness  is modeled as a finite state machine describ

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 2 Jun 2017 22:32, "Telmo Menezes"  wrote:

On Fri, Jun 2, 2017 at 5:53 PM, David Nyman  wrote:
> On 2 June 2017 at 14:34, Telmo Menezes  wrote:
>>
>> On Fri, Jun 2, 2017 at 3:21 PM, David Nyman 
wrote:
>> >
>> >
>> > On 2 Jun 2017 14:02, "Telmo Menezes"  wrote:
>> >
>> > On Fri, Jun 2, 2017 at 2:07 AM, Bruce Kellett
>> > 
>> > wrote:
>> >> On 2/06/2017 7:28 am, smitra wrote:
>> >>>
>> >>> On 01-06-2017 02:26, Bruce Kellett wrote:
>> 
>>  On 1/06/2017 4:43 am, Bruno Marchal wrote:
>> 
>>  Non-locality is not removed in MWI as you appear to believe.
>> 
>> > For me the abandon of the collapse is the solution of the EPR
>> > "paradox",
>> > and Aspect experience is somehow the confirmation of our belonging
>> > to
>> > macrosuperposition.
>> 
>> 
>>  The non-local (paradoxical) nature of EPR remains even without
>>  collapse. As on the previous occasion we discussed this, you were
>>  unable to demonstrate where the notion of 'collapse' is used in
>>  Bell's
>>  theorem - all Bell requires is that measurements give results, and
>>  that is what the whole of physics is based on: in MWI as well as in
>>  any other interpretation.
>> 
>>  Bruce
>> >>>
>> >>>
>> >>> In the MWI there are only trivial common cause like effects. There is
>> >>> no
>> >>> non-locality in some mysterious sense like there is in the CI where
>> >>> somehow
>> >>> there is a non-local effect but you don;t have information transfer.
>> >>> The
>> >>> mistake most people make when arguing that the MWI doesn't resolve
the
>> >>> problem is that they can't get their head around the fact that even
>> >>> when
>> >>> Alice and Bob meet and Alice has not yet communicated everything
>> >>> that's
>> >>> necessary to Bob, that the Alice that Bob sees has yet to collapse in
>> >>> the
>> >>> branch corresponding to whatever she is going to say (Bob's
>> >>> consciousness
>> >>> is
>> >>> thus located in many different branches of Alice, even if the atoms
in
>> >>> his
>> >>> body will be in different states due to decoherence).
>> >>
>> >>
>> >> I think that either you or someone else said something like this when
>> >> this
>> >> was last discussed. I have a couple of points to make:
>> >>
>> >> 1. This is not quantum mechanics, or the many worlds interpretation of
>> >> QM.
>> >> It is your own idiosyncratic theory that has no bearing on the
question
>> >> of
>> >> non-locality in QM.
>> >>
>> >> 2. Even in its own terms, this theory is nothing more than an
>> >> undisguised
>> >> appeal to magic. You want consciousness to be unrelated to the
>> >> decohered
>> >> body. That conflicts with the overwhelming experimental evidence in
>> >> favour
>> >> of the supervenience on consciousness on the physical brain
>> >
>> > I don't see how such experimental evidence can be claimed to exist,
>> > given that there is no way to measure consciousness.
>> >
>>
>> Hi David,
>>
>> > I think this is confused by an ambiguity about supervenience that I
>> > recently
>> > posted about. In the sense that one's own consciousness can be
>> > demonstrated
>> > to covary systematically with neurological function, there is surely no
>> > lack
>> > of experimental evidence.
>>
>> I've had this discussion with Brent a few times. Even in this case I
>> disagree that there is evidence. There is plenty of evidence that what
>> one can experience is correlated with brain states, but if you give me
>> anestesia and ask me if I was conscious, all I can really say is: "I
>> can't remember".
>>
>> Being conscious but not able to form memories is a well known
>> phenomena, because it is possible to detect REM sleep stages and brain
>> activity during dreaming, but sometimes people cannot remember
>> dreaming.
>>
>> These discussions are confused by the same word having multiple
>> meanings. The overloading of these meanings betrays hidden
>> assumptions, and I claim that we must bring these assumptions to the
>> light of day if we are going to be rigorous.
>
>
> Sure, but I don't see that anything you've said above is inconsistent with
> any particular state of consciousness supervening, in the simple sense of
> covariance stated above, with neurological function to any arbitrary level
> of detail.

Ok, in the simple sense of covariance I agree. Ant viable theory of
mind must explain why certain states of consciousness are correlated
with certain patterns of neural activity.

> Nor for that matter would it be necessary to deny this whatever
> one's preferred theory of consciousness might ultimately be (e.g.
> computationalism).

Agreed.

>>
>> > In the larger sense, of any finally unambiguous
>> > explanatory relation between the two phenomena in general, the question
>> > of
>> > evidence then depends rather upon what one is willing to count as
>> > explanation. The latter consideration is to say the least both less
>> > obvious
>> > and more controversial.
>>
>> I would say that it depends m

Re: A thought on MWI and its alternative(s)

[smitra]

On 02-06-2017 10:05, Bruce Kellett wrote:

On 2/06/2017 5:31 pm, smitra wrote:

On 02-06-2017 04:54, Bruce Kellett wrote:

On 2/06/2017 12:00 pm, smitra wrote:

On 02-06-2017 02:07, Bruce Kellett wrote:

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation of 
our belonging to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in 
Bell's
theorem - all Bell requires is that measurements give results, 
and
that is what the whole of physics is based on: in MWI as well as 
in

any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. There 
is no non-locality in some mysterious sense like there is in the 
CI where somehow there is a non-local effect but you don;t have 
information transfer. The mistake most people make when arguing 
that the MWI doesn't resolve the problem is that they can't get 
their head around the fact that even when Alice and Bob meet and 
Alice has not yet communicated everything that's necessary to Bob, 
that the Alice that Bob sees has yet to collapse in the branch 
corresponding to whatever she is going to say (Bob's consciousness 
is thus located in many different branches of Alice, even if the 
atoms in his body will be in different states due to decoherence).


I think that either you or someone else said something like this 
when

this was last discussed. I have a couple of points to make:

1. This is not quantum mechanics, or the many worlds interpretation 
of

QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.

2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be unrelated 
to
the decohered body. That conflicts with the overwhelming 
experimental

evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has 
decohered
having obtained a particular measurement result, all copies (if 
there
be such) of this consciousness are conscious of the same 
measurement
result. By the identity of indiscernibles, there is then only one 
body

and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.

Bruce




Suppose Alice and Bob are robots with classical processors, the 
states of each register can only be 0 and 1. Whatever Bob is 
conscious of must then be contained in the bitstring that specifies 
the state his processor is in. Decoherence has  no effect on that 
bitstring. Until that time that Bob asks Alice about her setting of 
her polarizer, Bob's consciousness is exactly the same across the 
different branches in which Alice gives a different answer,


False.


It's trivially true.


Bob's consciousness reflects the results he got. There are only four
branches: '++', '+-', '-+', and '--'. Bob's conscious state is
different for the two Alice '+' branches, and also different for the
two Alice '-' branches. So it is not invariant across Alice's
branches.


What  matters for the MWI discussion is simply that after Bob has made 
his measurement and he gets located in a branch corresponding to 
whatever he has measured, that whatever Alice does is not going to 
further localize Bob in a narrower set of branches due to decoherence 
caused by Alice's measurements. Here you then do need to extract Bob's 
consciousness from Bob's exact physical state. It's only when Alice 
communicates the details that Bob's consciousness get's located in 
Alice's branches.





despite rapid decoherence.

Real human beings can be expected to fit well within this model. It 
is known that there typically is a lot of information present in the 
unconscious mind that we're not aware of. So, your consciousness 
could be identical across many branches even if your brain had split 
and the unconscious mind is already diverging. Take e.g. experiments 
where you are making a random choice and on the basis on functional 
MRI scans the experimenters are able to predict your choice before 
you have even made up your mind.


So, this is same good old QM in the MWI where an observer's 
consciousness  is modeled as a finite state machine described by a 
finite bitstring. We can then work in the basis where the 
observables for the bits of the bitstrings are all diagonal, this 
then corresponds to the observer having a definite conscious 
experience.


The definite conscious experience of relevance here is of observing
and recording the result of the spin measurement.

In practice, what this means is that you can be in a macroscopic 
superposition long after decoheren

Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

On Fri, Jun 2, 2017 at 5:53 PM, David Nyman  wrote:
> On 2 June 2017 at 14:34, Telmo Menezes  wrote:
>>
>> On Fri, Jun 2, 2017 at 3:21 PM, David Nyman  wrote:
>> >
>> >
>> > On 2 Jun 2017 14:02, "Telmo Menezes"  wrote:
>> >
>> > On Fri, Jun 2, 2017 at 2:07 AM, Bruce Kellett
>> > 
>> > wrote:
>> >> On 2/06/2017 7:28 am, smitra wrote:
>> >>>
>> >>> On 01-06-2017 02:26, Bruce Kellett wrote:
>> 
>>  On 1/06/2017 4:43 am, Bruno Marchal wrote:
>> 
>>  Non-locality is not removed in MWI as you appear to believe.
>> 
>> > For me the abandon of the collapse is the solution of the EPR
>> > "paradox",
>> > and Aspect experience is somehow the confirmation of our belonging
>> > to
>> > macrosuperposition.
>> 
>> 
>>  The non-local (paradoxical) nature of EPR remains even without
>>  collapse. As on the previous occasion we discussed this, you were
>>  unable to demonstrate where the notion of 'collapse' is used in
>>  Bell's
>>  theorem - all Bell requires is that measurements give results, and
>>  that is what the whole of physics is based on: in MWI as well as in
>>  any other interpretation.
>> 
>>  Bruce
>> >>>
>> >>>
>> >>> In the MWI there are only trivial common cause like effects. There is
>> >>> no
>> >>> non-locality in some mysterious sense like there is in the CI where
>> >>> somehow
>> >>> there is a non-local effect but you don;t have information transfer.
>> >>> The
>> >>> mistake most people make when arguing that the MWI doesn't resolve the
>> >>> problem is that they can't get their head around the fact that even
>> >>> when
>> >>> Alice and Bob meet and Alice has not yet communicated everything
>> >>> that's
>> >>> necessary to Bob, that the Alice that Bob sees has yet to collapse in
>> >>> the
>> >>> branch corresponding to whatever she is going to say (Bob's
>> >>> consciousness
>> >>> is
>> >>> thus located in many different branches of Alice, even if the atoms in
>> >>> his
>> >>> body will be in different states due to decoherence).
>> >>
>> >>
>> >> I think that either you or someone else said something like this when
>> >> this
>> >> was last discussed. I have a couple of points to make:
>> >>
>> >> 1. This is not quantum mechanics, or the many worlds interpretation of
>> >> QM.
>> >> It is your own idiosyncratic theory that has no bearing on the question
>> >> of
>> >> non-locality in QM.
>> >>
>> >> 2. Even in its own terms, this theory is nothing more than an
>> >> undisguised
>> >> appeal to magic. You want consciousness to be unrelated to the
>> >> decohered
>> >> body. That conflicts with the overwhelming experimental evidence in
>> >> favour
>> >> of the supervenience on consciousness on the physical brain
>> >
>> > I don't see how such experimental evidence can be claimed to exist,
>> > given that there is no way to measure consciousness.
>> >
>>
>> Hi David,
>>
>> > I think this is confused by an ambiguity about supervenience that I
>> > recently
>> > posted about. In the sense that one's own consciousness can be
>> > demonstrated
>> > to covary systematically with neurological function, there is surely no
>> > lack
>> > of experimental evidence.
>>
>> I've had this discussion with Brent a few times. Even in this case I
>> disagree that there is evidence. There is plenty of evidence that what
>> one can experience is correlated with brain states, but if you give me
>> anestesia and ask me if I was conscious, all I can really say is: "I
>> can't remember".
>>
>> Being conscious but not able to form memories is a well known
>> phenomena, because it is possible to detect REM sleep stages and brain
>> activity during dreaming, but sometimes people cannot remember
>> dreaming.
>>
>> These discussions are confused by the same word having multiple
>> meanings. The overloading of these meanings betrays hidden
>> assumptions, and I claim that we must bring these assumptions to the
>> light of day if we are going to be rigorous.
>
>
> Sure, but I don't see that anything you've said above is inconsistent with
> any particular state of consciousness supervening, in the simple sense of
> covariance stated above, with neurological function to any arbitrary level
> of detail.

Ok, in the simple sense of covariance I agree. Ant viable theory of
mind must explain why certain states of consciousness are correlated
with certain patterns of neural activity.

> Nor for that matter would it be necessary to deny this whatever
> one's preferred theory of consciousness might ultimately be (e.g.
> computationalism).

Agreed.

>>
>> > In the larger sense, of any finally unambiguous
>> > explanatory relation between the two phenomena in general, the question
>> > of
>> > evidence then depends rather upon what one is willing to count as
>> > explanation. The latter consideration is to say the least both less
>> > obvious
>> > and more controversial.
>>
>> I would say that it depends more on what one is willing to count as
>> evid

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 2 June 2017 at 20:14, Brent Meeker  wrote:

>
>
> On 6/2/2017 12:01 PM, David Nyman wrote:
>
>
>
> On 2 Jun 2017 19:18, "Brent Meeker"  wrote:
>
>
>
> On 6/2/2017 6:21 AM, David Nyman wrote:
>
> I don't see how such experimental evidence can be claimed to exist,
> given that there is no way to measure consciousness.
>
>
> I think this is confused by an ambiguity about supervenience that I
> recently posted about. In the sense that one's own consciousness can be
> demonstrated to covary systematically with neurological function, there is
> surely no lack of experimental evidence. In the larger sense, of any
> finally unambiguous explanatory relation between the two phenomena in
> general, the question of evidence then depends rather upon what one is
> willing to count as explanation. The latter consideration is to say the
> least both less obvious and more controversial.
>
>
> Right.  And a point I've tried to make (apparently unsuccessfully) several
> times.
>
>
> Not so. I have always accepted your view as one of the essential
> components of any explanation (i. e. the covariance part).
>
>   In the case of physical phenomena, like gravity, we arrive at a
> mathematical model and we're all happy - we've explained gravity.  When we
> do the same thing, providing a useful model of the brain that predicts
> conscious thoughts (cf. electrostimulation during brain surgery) we should
> be happy that we've explained consciousness.  But NO, there are all the
> philosophers dedicated to "the hard problem" who demand to know  "what
> really makes consciousness?".  The analogy in physics is John Archibald
> Wheeler asking, "But what makes the equations *fly*?"
>
> In the virtuous circle of explanation, if you're not willing to count
> anything as an explanation, then there is no explanation.
>
>
> Again not so. An explanation of consciousness in terms of neurocognition
> is both ineliminable and indispensable from a practical perspective. But
> left at that, any explanatory relation with first person subjectivity can
> never be more than an a posteriori attribution. After all, an explicit
> account in terms of neurocognition is already causally sufficient in its
> own right.
>
> IMO the so-called hard problem is an unfortunate artifact of a faulty
> formulation of the problem area. Consequently comp doesn't try to 'solve'
> it. Instead, it recasts the problem in essentially epistemological terms,
> relying on the simplest assumptive ontology adequate to the task. To
> succeed, it must also show that this manner of framing the problem is fully
> compatible with an observable physics (and its theoretical ontology) such
> that all aspects of the physical covariance remarked on above remain
> consistent. All that said, what bears most heavily on its role in
> explanation is to offer, a priori, an otherwise absent first-personal
> account of the characteristic phenomena of subjectivity.
>
>
> I find we are in violent agreement.  :-)
>

​Excellent. I think if we can somehow contrive to retain some memory of
this mutual accommodation (difficult as I know that can be with our
advancing years!) we may in future reach a better understanding of where we
may still possibly diverge. As ever, I value your comments and analysis in
correcting my own views.

David

>
>
> Brent
>

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Re: A thought on MWI and its alternative(s)

[David Nyman]

On 2 June 2017 at 14:34, Telmo Menezes  wrote:

> On Fri, Jun 2, 2017 at 3:21 PM, David Nyman  wrote:
> >
> >
> > On 2 Jun 2017 14:02, "Telmo Menezes"  wrote:
> >
> > On Fri, Jun 2, 2017 at 2:07 AM, Bruce Kellett  >
> > wrote:
> >> On 2/06/2017 7:28 am, smitra wrote:
> >>>
> >>> On 01-06-2017 02:26, Bruce Kellett wrote:
> 
>  On 1/06/2017 4:43 am, Bruno Marchal wrote:
> 
>  Non-locality is not removed in MWI as you appear to believe.
> 
> > For me the abandon of the collapse is the solution of the EPR
> > "paradox",
> > and Aspect experience is somehow the confirmation of our belonging
> to
> > macrosuperposition.
> 
> 
>  The non-local (paradoxical) nature of EPR remains even without
>  collapse. As on the previous occasion we discussed this, you were
>  unable to demonstrate where the notion of 'collapse' is used in Bell's
>  theorem - all Bell requires is that measurements give results, and
>  that is what the whole of physics is based on: in MWI as well as in
>  any other interpretation.
> 
>  Bruce
> >>>
> >>>
> >>> In the MWI there are only trivial common cause like effects. There is
> no
> >>> non-locality in some mysterious sense like there is in the CI where
> >>> somehow
> >>> there is a non-local effect but you don;t have information transfer.
> The
> >>> mistake most people make when arguing that the MWI doesn't resolve the
> >>> problem is that they can't get their head around the fact that even
> when
> >>> Alice and Bob meet and Alice has not yet communicated everything
> that's
> >>> necessary to Bob, that the Alice that Bob sees has yet to collapse in
> the
> >>> branch corresponding to whatever she is going to say (Bob's
> consciousness
> >>> is
> >>> thus located in many different branches of Alice, even if the atoms in
> >>> his
> >>> body will be in different states due to decoherence).
> >>
> >>
> >> I think that either you or someone else said something like this when
> this
> >> was last discussed. I have a couple of points to make:
> >>
> >> 1. This is not quantum mechanics, or the many worlds interpretation of
> QM.
> >> It is your own idiosyncratic theory that has no bearing on the question
> of
> >> non-locality in QM.
> >>
> >> 2. Even in its own terms, this theory is nothing more than an
> undisguised
> >> appeal to magic. You want consciousness to be unrelated to the decohered
> >> body. That conflicts with the overwhelming experimental evidence in
> favour
> >> of the supervenience on consciousness on the physical brain
> >
> > I don't see how such experimental evidence can be claimed to exist,
> > given that there is no way to measure consciousness.
> >
>
> Hi David,
>
> > I think this is confused by an ambiguity about supervenience that I
> recently
> > posted about. In the sense that one's own consciousness can be
> demonstrated
> > to covary systematically with neurological function, there is surely no
> lack
> > of experimental evidence.
>
> I've had this discussion with Brent a few times. Even in this case I
> disagree that there is evidence. There is plenty of evidence that what
> one can experience is correlated with brain states, but if you give me
> anestesia and ask me if I was conscious, all I can really say is: "I
> can't remember".
>
> Being conscious but not able to form memories is a well known
> phenomena, because it is possible to detect REM sleep stages and brain
> activity during dreaming, but sometimes people cannot remember
> dreaming.
>
> These discussions are confused by the same word having multiple
> meanings. The overloading of these meanings betrays hidden
> assumptions, and I claim that we must bring these assumptions to the
> light of day if we are going to be rigorous.
>

​Sure, but I don't see that anything you've said above is inconsistent with
any particular state of consciousness supervening, in the simple sense of
covariance stated above, with neurological function to any arbitrary level
of detail. Nor for that matter would it be necessary to deny this whatever
one's preferred theory of consciousness might ultimately be (e.g.
computationalism).


> > In the larger sense, of any finally unambiguous
> > explanatory relation between the two phenomena in general, the question
> of
> > evidence then depends rather upon what one is willing to count as
> > explanation. The latter consideration is to say the least both less
> obvious
> > and more controversial.
>
> I would say that it depends more on what one is willing to count as
> evidence.


​Well, what would count as evidence is intimately linked to what would
count as explanation, since what is selected in the first instance as data
is closely dependent on the dictates of theory.

Indirect measures of consciousness entail hidden
> assumptions, and it becomes easy to beg the question.
>

​Which particular question did you have in mind?

David​

>
> Telmo.
>
> > David
> >
> > In my opinion this results from equating in

Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

On Fri, Jun 2, 2017 at 3:21 PM, David Nyman  wrote:
>
>
> On 2 Jun 2017 14:02, "Telmo Menezes"  wrote:
>
> On Fri, Jun 2, 2017 at 2:07 AM, Bruce Kellett 
> wrote:
>> On 2/06/2017 7:28 am, smitra wrote:
>>>
>>> On 01-06-2017 02:26, Bruce Kellett wrote:

 On 1/06/2017 4:43 am, Bruno Marchal wrote:

 Non-locality is not removed in MWI as you appear to believe.

> For me the abandon of the collapse is the solution of the EPR
> "paradox",
> and Aspect experience is somehow the confirmation of our belonging  to
> macrosuperposition.


 The non-local (paradoxical) nature of EPR remains even without
 collapse. As on the previous occasion we discussed this, you were
 unable to demonstrate where the notion of 'collapse' is used in Bell's
 theorem - all Bell requires is that measurements give results, and
 that is what the whole of physics is based on: in MWI as well as in
 any other interpretation.

 Bruce
>>>
>>>
>>> In the MWI there are only trivial common cause like effects. There is no
>>> non-locality in some mysterious sense like there is in the CI where
>>> somehow
>>> there is a non-local effect but you don;t have information transfer. The
>>> mistake most people make when arguing that the MWI doesn't resolve the
>>> problem is that they can't get their head around the fact that even when
>>> Alice and Bob meet and Alice has not yet communicated everything  that's
>>> necessary to Bob, that the Alice that Bob sees has yet to collapse in the
>>> branch corresponding to whatever she is going to say (Bob's consciousness
>>> is
>>> thus located in many different branches of Alice, even if the atoms in
>>> his
>>> body will be in different states due to decoherence).
>>
>>
>> I think that either you or someone else said something like this when this
>> was last discussed. I have a couple of points to make:
>>
>> 1. This is not quantum mechanics, or the many worlds interpretation of QM.
>> It is your own idiosyncratic theory that has no bearing on the question of
>> non-locality in QM.
>>
>> 2. Even in its own terms, this theory is nothing more than an undisguised
>> appeal to magic. You want consciousness to be unrelated to the decohered
>> body. That conflicts with the overwhelming experimental evidence in favour
>> of the supervenience on consciousness on the physical brain
>
> I don't see how such experimental evidence can be claimed to exist,
> given that there is no way to measure consciousness.
>

Hi David,

> I think this is confused by an ambiguity about supervenience that I recently
> posted about. In the sense that one's own consciousness can be demonstrated
> to covary systematically with neurological function, there is surely no lack
> of experimental evidence.

I've had this discussion with Brent a few times. Even in this case I
disagree that there is evidence. There is plenty of evidence that what
one can experience is correlated with brain states, but if you give me
anestesia and ask me if I was conscious, all I can really say is: "I
can't remember".

Being conscious but not able to form memories is a well known
phenomena, because it is possible to detect REM sleep stages and brain
activity during dreaming, but sometimes people cannot remember
dreaming.

These discussions are confused by the same word having multiple
meanings. The overloading of these meanings betrays hidden
assumptions, and I claim that we must bring these assumptions to the
light of day if we are going to be rigorous.

> In the larger sense, of any finally unambiguous
> explanatory relation between the two phenomena in general, the question of
> evidence then depends rather upon what one is willing to count as
> explanation. The latter consideration is to say the least both less obvious
> and more controversial.

I would say that it depends more on what one is willing to count as
evidence. Indirect measures of consciousness entail hidden
assumptions, and it becomes easy to beg the question.

Telmo.

> David
>
> In my opinion this results from equating intelligence and human
> experience with consciousness. Maybe that position is correct, but
> nobody can claim to know if this is the case.
>
> There is overwhelming evidence that the physical brain is a computer,
> capable of storing memories, detecting patterns, predicting the future
> and so on. It is also the case that human experience depends on these
> mechanisms. What there is no evidence for is what is conscious or not.
>
> For example, panpsychists hold that everything is conscious. I don't
> see how such a hypothesis can be falsified at the moment.
>
> Telmo.
>
>> -- they move in
>> lockstep, so if your body has decohered having obtained a particular
>> measurement result, all copies (if there be such) of this consciousness
>> are
>> conscious of the same measurement result. By the identity of
>> indiscernibles,
>> there is then only one body and one consciousness. That is what QM and MWI
>> tell y

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 2 Jun 2017 14:02, "Telmo Menezes"  wrote:

On Fri, Jun 2, 2017 at 2:07 AM, Bruce Kellett 
wrote:
> On 2/06/2017 7:28 am, smitra wrote:
>>
>> On 01-06-2017 02:26, Bruce Kellett wrote:
>>>
>>> On 1/06/2017 4:43 am, Bruno Marchal wrote:
>>>
>>> Non-locality is not removed in MWI as you appear to believe.
>>>
 For me the abandon of the collapse is the solution of the EPR
"paradox",
 and Aspect experience is somehow the confirmation of our belonging  to
 macrosuperposition.
>>>
>>>
>>> The non-local (paradoxical) nature of EPR remains even without
>>> collapse. As on the previous occasion we discussed this, you were
>>> unable to demonstrate where the notion of 'collapse' is used in Bell's
>>> theorem - all Bell requires is that measurements give results, and
>>> that is what the whole of physics is based on: in MWI as well as in
>>> any other interpretation.
>>>
>>> Bruce
>>
>>
>> In the MWI there are only trivial common cause like effects. There is no
>> non-locality in some mysterious sense like there is in the CI where
somehow
>> there is a non-local effect but you don;t have information transfer. The
>> mistake most people make when arguing that the MWI doesn't resolve the
>> problem is that they can't get their head around the fact that even when
>> Alice and Bob meet and Alice has not yet communicated everything  that's
>> necessary to Bob, that the Alice that Bob sees has yet to collapse in the
>> branch corresponding to whatever she is going to say (Bob's
consciousness is
>> thus located in many different branches of Alice, even if the atoms in
his
>> body will be in different states due to decoherence).
>
>
> I think that either you or someone else said something like this when this
> was last discussed. I have a couple of points to make:
>
> 1. This is not quantum mechanics, or the many worlds interpretation of QM.
> It is your own idiosyncratic theory that has no bearing on the question of
> non-locality in QM.
>
> 2. Even in its own terms, this theory is nothing more than an undisguised
> appeal to magic. You want consciousness to be unrelated to the decohered
> body. That conflicts with the overwhelming experimental evidence in favour
> of the supervenience on consciousness on the physical brain

I don't see how such experimental evidence can be claimed to exist,
given that there is no way to measure consciousness.


I think this is confused by an ambiguity about supervenience that I
recently posted about. In the sense that one's own consciousness can be
demonstrated to covary systematically with neurological function, there is
surely no lack of experimental evidence. In the larger sense, of any
finally unambiguous explanatory relation between the two phenomena in
general, the question of evidence then depends rather upon what one is
willing to count as explanation. The latter consideration is to say the
least both less obvious and more controversial.

David

In my opinion this results from equating intelligence and human
experience with consciousness. Maybe that position is correct, but
nobody can claim to know if this is the case.

There is overwhelming evidence that the physical brain is a computer,
capable of storing memories, detecting patterns, predicting the future
and so on. It is also the case that human experience depends on these
mechanisms. What there is no evidence for is what is conscious or not.

For example, panpsychists hold that everything is conscious. I don't
see how such a hypothesis can be falsified at the moment.

Telmo.

> -- they move in
> lockstep, so if your body has decohered having obtained a particular
> measurement result, all copies (if there be such) of this consciousness
are
> conscious of the same measurement result. By the identity of
indiscernibles,
> there is then only one body and one consciousness. That is what QM and MWI
> tell you, any deviations are simple fantasy.
>
> Bruce
>
>
>
>> The apparent non-locality is then purely an artifact on making such
>> assumptions about localization in branches when that's wrong to do.
>>
>> Saibal
>>
>
> --
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Re: A thought on MWI and its alternative(s)

[Telmo Menezes]

On Fri, Jun 2, 2017 at 2:07 AM, Bruce Kellett  wrote:
> On 2/06/2017 7:28 am, smitra wrote:
>>
>> On 01-06-2017 02:26, Bruce Kellett wrote:
>>>
>>> On 1/06/2017 4:43 am, Bruno Marchal wrote:
>>>
>>> Non-locality is not removed in MWI as you appear to believe.
>>>
 For me the abandon of the collapse is the solution of the EPR "paradox",
 and Aspect experience is somehow the confirmation of our belonging  to
 macrosuperposition.
>>>
>>>
>>> The non-local (paradoxical) nature of EPR remains even without
>>> collapse. As on the previous occasion we discussed this, you were
>>> unable to demonstrate where the notion of 'collapse' is used in Bell's
>>> theorem - all Bell requires is that measurements give results, and
>>> that is what the whole of physics is based on: in MWI as well as in
>>> any other interpretation.
>>>
>>> Bruce
>>
>>
>> In the MWI there are only trivial common cause like effects. There is no
>> non-locality in some mysterious sense like there is in the CI where somehow
>> there is a non-local effect but you don;t have information transfer. The
>> mistake most people make when arguing that the MWI doesn't resolve the
>> problem is that they can't get their head around the fact that even when
>> Alice and Bob meet and Alice has not yet communicated everything  that's
>> necessary to Bob, that the Alice that Bob sees has yet to collapse in the
>> branch corresponding to whatever she is going to say (Bob's consciousness is
>> thus located in many different branches of Alice, even if the atoms in his
>> body will be in different states due to decoherence).
>
>
> I think that either you or someone else said something like this when this
> was last discussed. I have a couple of points to make:
>
> 1. This is not quantum mechanics, or the many worlds interpretation of QM.
> It is your own idiosyncratic theory that has no bearing on the question of
> non-locality in QM.
>
> 2. Even in its own terms, this theory is nothing more than an undisguised
> appeal to magic. You want consciousness to be unrelated to the decohered
> body. That conflicts with the overwhelming experimental evidence in favour
> of the supervenience on consciousness on the physical brain

I don't see how such experimental evidence can be claimed to exist,
given that there is no way to measure consciousness.
In my opinion this results from equating intelligence and human
experience with consciousness. Maybe that position is correct, but
nobody can claim to know if this is the case.

There is overwhelming evidence that the physical brain is a computer,
capable of storing memories, detecting patterns, predicting the future
and so on. It is also the case that human experience depends on these
mechanisms. What there is no evidence for is what is conscious or not.

For example, panpsychists hold that everything is conscious. I don't
see how such a hypothesis can be falsified at the moment.

Telmo.

> -- they move in
> lockstep, so if your body has decohered having obtained a particular
> measurement result, all copies (if there be such) of this consciousness are
> conscious of the same measurement result. By the identity of indiscernibles,
> there is then only one body and one consciousness. That is what QM and MWI
> tell you, any deviations are simple fantasy.
>
> Bruce
>
>
>
>> The apparent non-locality is then purely an artifact on making such
>> assumptions about localization in branches when that's wrong to do.
>>
>> Saibal
>>
>
> --
> You received this message because you are subscribed to the Google Groups
> "Everything List" group.
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> email to everything-list+unsubscr...@googlegroups.com.
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Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 2/06/2017 5:31 pm, smitra wrote:

On 02-06-2017 04:54, Bruce Kellett wrote:

On 2/06/2017 12:00 pm, smitra wrote:

On 02-06-2017 02:07, Bruce Kellett wrote:

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation of 
our belonging to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in 
Bell's

theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as in
any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. There 
is no non-locality in some mysterious sense like there is in the 
CI where somehow there is a non-local effect but you don;t have 
information transfer. The mistake most people make when arguing 
that the MWI doesn't resolve the problem is that they can't get 
their head around the fact that even when Alice and Bob meet and 
Alice has not yet communicated everything that's necessary to Bob, 
that the Alice that Bob sees has yet to collapse in the branch 
corresponding to whatever she is going to say (Bob's consciousness 
is thus located in many different branches of Alice, even if the 
atoms in his body will be in different states due to decoherence).


I think that either you or someone else said something like this when
this was last discussed. I have a couple of points to make:

1. This is not quantum mechanics, or the many worlds interpretation of
QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.

2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be unrelated to
the decohered body. That conflicts with the overwhelming experimental
evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has decohered
having obtained a particular measurement result, all copies (if there
be such) of this consciousness are conscious of the same measurement
result. By the identity of indiscernibles, there is then only one body
and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.

Bruce




Suppose Alice and Bob are robots with classical processors, the 
states of each register can only be 0 and 1. Whatever Bob is 
conscious of must then be contained in the bitstring that specifies 
the state his processor is in. Decoherence has  no effect on that 
bitstring. Until that time that Bob asks Alice about her setting of 
her polarizer, Bob's consciousness is exactly the same across the 
different branches in which Alice gives a different answer,


False.


It's trivially true.


Bob's consciousness reflects the results he got. There are only four 
branches: '++', '+-', '-+', and '--'. Bob's conscious state is different 
for the two Alice '+' branches, and also different for the two Alice '-' 
branches. So it is not invariant across Alice's branches.



despite rapid decoherence.

Real human beings can be expected to fit well within this model. It 
is known that there typically is a lot of information present in the 
unconscious mind that we're not aware of. So, your consciousness 
could be identical across many branches even if your brain had split 
and the unconscious mind is already diverging. Take e.g. experiments 
where you are making a random choice and on the basis on functional 
MRI scans the experimenters are able to predict your choice before 
you have even made up your mind.


So, this is same good old QM in the MWI where an observer's 
consciousness  is modeled as a finite state machine described by a 
finite bitstring. We can then work in the basis where the 
observables for the bits of the bitstrings are all diagonal, this 
then corresponds to the observer having a definite conscious 
experience.


The definite conscious experience of relevance here is of observing
and recording the result of the spin measurement.

In practice, what this means is that you can be in a macroscopic 
superposition long after decoherence has for all practical purposes 
made the superposition inaccessible to be probed using interference 
or other experiments.


For example, if a spin is polarized in the positive x-direction and 
the z-component is measured, and I'm not aware of the outcome of the 
result then my consciousness, as specified by the bitstring that 
contains all the information that I'm aware of,  cannot possibly 
contain the result of the outcome of the measurement before I'm told 
what the result is.


 In a sector where my consciousness is described by bitstring X 
after 

Re: A thought on MWI and its alternative(s)

[smitra]

On 02-06-2017 04:54, Bruce Kellett wrote:

On 2/06/2017 12:00 pm, smitra wrote:

On 02-06-2017 02:07, Bruce Kellett wrote:

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation of 
our belonging to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in 
Bell's

theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as in
any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. There 
is no non-locality in some mysterious sense like there is in the CI 
where somehow there is a non-local effect but you don;t have 
information transfer. The mistake most people make when arguing that 
the MWI doesn't resolve the problem is that they can't get their 
head around the fact that even when Alice and Bob meet and Alice has 
not yet communicated everything that's necessary to Bob, that the 
Alice that Bob sees has yet to collapse in the branch corresponding 
to whatever she is going to say (Bob's consciousness is thus located 
in many different branches of Alice, even if the atoms in his body 
will be in different states due to decoherence).


I think that either you or someone else said something like this when
this was last discussed. I have a couple of points to make:

1. This is not quantum mechanics, or the many worlds interpretation 
of

QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.

2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be unrelated 
to

the decohered body. That conflicts with the overwhelming experimental
evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has 
decohered

having obtained a particular measurement result, all copies (if there
be such) of this consciousness are conscious of the same measurement
result. By the identity of indiscernibles, there is then only one 
body

and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.

Bruce




Suppose Alice and Bob are robots with classical processors, the states 
of each register can only be 0 and 1. Whatever Bob is conscious of 
must then be contained in the bitstring that specifies the state his 
processor is in. Decoherence has  no effect on that bitstring. Until 
that time that Bob asks Alice about her setting of her polarizer, 
Bob's consciousness is exactly the same across the different branches 
in which Alice gives a different answer,


False.


It's trivially true.





despite rapid decoherence.

Real human beings can be expected to fit well within this model. It is 
known that there typically is a lot of information present in the 
unconscious mind that we're not aware of. So, your consciousness could 
be identical across many branches even if your brain had split and the 
unconscious mind is already diverging. Take e.g. experiments where you 
are making a random choice and on the basis on functional MRI scans 
the experimenters are able to predict your choice before you have even 
made up your mind.


So, this is same good old QM in the MWI where an observer's 
consciousness  is modeled as a finite state machine described by a 
finite bitstring. We can then work in the basis where the observables 
for the bits of the bitstrings are all diagonal, this then corresponds 
to the observer having a definite conscious experience.


The definite conscious experience of relevance here is of observing
and recording the result of the spin measurement.

In practice, what this means is that you can be in a macroscopic 
superposition long after decoherence has for all practical purposes 
made the superposition inaccessible to be probed using interference or 
other experiments.


For example, if a spin is polarized in the positive x-direction and 
the z-component is measured, and I'm not aware of the outcome of the 
result then my consciousness, as specified by the bitstring that 
contains all the information that I'm aware of,  cannot possibly 
contain the result of the outcome of the measurement before I'm told 
what the result is.


 In a sector where my consciousness is described by bitstring X after 
the spin has been measured, the state will have to be of the form:


1/sqrt(2) |X> [|up, Universe(up)> + |down, Universe(down> ]

where Universe(up)  and Universe(down) are different states of the 
rest of the universe, but my consciousness is described by X and this 
is not affected by the decoherence ca

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 2/06/2017 12:00 pm, smitra wrote:

On 02-06-2017 02:07, Bruce Kellett wrote:

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation of 
our belonging to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in Bell's
theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as in
any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. There 
is no non-locality in some mysterious sense like there is in the CI 
where somehow there is a non-local effect but you don;t have 
information transfer. The mistake most people make when arguing that 
the MWI doesn't resolve the problem is that they can't get their 
head around the fact that even when Alice and Bob meet and Alice has 
not yet communicated everything that's necessary to Bob, that the 
Alice that Bob sees has yet to collapse in the branch corresponding 
to whatever she is going to say (Bob's consciousness is thus located 
in many different branches of Alice, even if the atoms in his body 
will be in different states due to decoherence).


I think that either you or someone else said something like this when
this was last discussed. I have a couple of points to make:

1. This is not quantum mechanics, or the many worlds interpretation of
QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.

2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be unrelated to
the decohered body. That conflicts with the overwhelming experimental
evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has decohered
having obtained a particular measurement result, all copies (if there
be such) of this consciousness are conscious of the same measurement
result. By the identity of indiscernibles, there is then only one body
and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.

Bruce




Suppose Alice and Bob are robots with classical processors, the states 
of each register can only be 0 and 1. Whatever Bob is conscious of 
must then be contained in the bitstring that specifies the state his 
processor is in. Decoherence has  no effect on that bitstring. Until 
that time that Bob asks Alice about her setting of her polarizer, 
Bob's consciousness is exactly the same across the different branches 
in which Alice gives a different answer,


False.


despite rapid decoherence.

Real human beings can be expected to fit well within this model. It is 
known that there typically is a lot of information present in the 
unconscious mind that we're not aware of. So, your consciousness could 
be identical across many branches even if your brain had split and the 
unconscious mind is already diverging. Take e.g. experiments where you 
are making a random choice and on the basis on functional MRI scans 
the experimenters are able to predict your choice before you have even 
made up your mind.


So, this is same good old QM in the MWI where an observer's 
consciousness  is modeled as a finite state machine described by a 
finite bitstring. We can then work in the basis where the observables 
for the bits of the bitstrings are all diagonal, this then corresponds 
to the observer having a definite conscious experience.


The definite conscious experience of relevance here is of observing and 
recording the result of the spin measurement.


In practice, what this means is that you can be in a macroscopic 
superposition long after decoherence has for all practical purposes 
made the superposition inaccessible to be probed using interference or 
other experiments.


For example, if a spin is polarized in the positive x-direction and 
the z-component is measured, and I'm not aware of the outcome of the 
result then my consciousness, as specified by the bitstring that 
contains all the information that I'm aware of,  cannot possibly 
contain the result of the outcome of the measurement before I'm told 
what the result is.


 In a sector where my consciousness is described by bitstring X after 
the spin has been measured, the state will have to be of the form:


1/sqrt(2) |X> [|up, Universe(up)> + |down, Universe(down> ]

where Universe(up)  and Universe(down) are different states of the 
rest of the universe, but my consciousness is described by X and this 
is not affected by the decoherence caused by measuring the spin. In 
general there will be a summation of such ter

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 1/06/2017 10:52 pm, Bruno Marchal wrote:

On 01 Jun 2017, at 13:02, Bruce Kellett wrote:

On 1/06/2017 8:21 pm, Bruno Marchal wrote:

On 31 May 2017, at 09:15, Bruce Kellett wrote:

On 31/05/2017 4:40 pm, Pierz wrote:


>> On 5/30/2017 7:30 PM, Pierz wrote:
>>> Thanks for these clarifications Bruce. I find your
explanations to be very lucid and helpful - they also confirm
my own understanding. IIRC, you weren't a particular fan of
MWI when I last conversed with you on this list. I wonder if
you'd care to comment on my original argument on this thread -
which has of course now been swamped by the usual brawls. Does
not a single history + the physical insignificance of the
notion of a current moment mean that there is also only a
single possible future?
>> I don't see how that follows.  In the usual model of
forking in the future direction every current moment has a
single history, but multiple futures.


Multiple futures = MWI, surely.


Not necessarily. If you insist on Schrödinger determinism, then 
yes, by reification of the wave function. But if the wave function 
is only epistemological, then there is only one probabilistic future.


How could an epistemological wave interfere all by itself? It seems 
simpler to say that the wave is real, but that the local, one 
branch, perception is epistemological.


I think you misunderstand this use of the word "epistemological". 
When it is said that the wave function is merely epistemological, 
what is meant that it is merely a calculational device: the wave 
function encapsulates our knowledge of the system of interest, and 
tells us how to calculate the probabilities of various outcomes. In 
other words, it is not a 'real' wave in space-time.


Yes. That is the problem. How a non real wave in space time can 
interfere really in space-time? Of course, the answer is simple with 
the MWI, but asks for real infuence at a distance with the Mono-world 
assumption.


The epistemological understanding does not have a non-real wave in 
space-time interfering in real space-time. It is merely a calculational 
device to get the QM probabilities, it doesn't interfere with anything. 
In MWI there is a real problem -- how can a complex wave existing in 
N-dimensional configuration space influence anything in 3-dimensional 
space-time?



When I say a single history, I mean that from the Big Bang 
forward, the universe only followed one branch.


And that can lead into the future, only one probabilistic future.


>>
>>> And if the future is predetermined in this way, isn't this
a serious issue for single universe models of QM? How can the
outcome of quantum events be both inevitable and random?
>> Having a single future isn't the same as being determined.
 A single future in which situation A is sometimes followed by
B and sometimes by C is still random.


It depends on perspective. It's true that from 1p, it looks 
random. But from 3p, it is static and always the same, and in this 
sense determined.


Not true, the 3p view of the future is still just a single 
probabilistic world line. It is only the bird view, from outside 
space and time, that gives the appearance that there are multiply 
existing futures. Neither we from the 1p perspective, or from 
outside ourselves in the 3p perspective, can we ever see any of the 
other branches predicted by MWI.


Yes, like in WM-duplication.


No, that is a serious mistake. Unitary evolution of the wave function 
is not at all like the person duplication experiments. The main 
difference is that the duplicates of the Helsinki man are never in a 
pure quantum state.


That was not the point. The comparison is on the reasult measurement, 
not on the reason of the parallel states. With mechanism, the reason 
are the same (the first person indeterminacy). With collapse, we need 
magic.


The teleportation to W or M is of separate classical entities, There 
is no superposition principle for duplicated persons.


You can defined for the Helsinki guy. He is in a sort of (non quantum) 
superposition state in helsinki, which indeed, like in the MWI, is 
just his ignoance on which computations he belongs. I use Y = II, if 
that is still needed to say.


Your attempt to draw a parallel between person duplication in a 
laboratory and MWI is simply causing confusion. They are in no way 
similar. There is no such thing as 'a sort of non quantum 
superposition'. That is just an abuse of language. Classical 
probabilities are completely unlike quantum superpositions.




The guy in Helsinki can predict that his first person future will be 
unique, even if he knows that in the "bird" picture, that outside 
the teleportation/duplication boxes, there will be two versions of him.


That is not the "bird" picture, that is merely the objective 3p 
picture of the ordinary classical world. The bird picture is solely 
to do with the pure state that is preserved in the unitary

Re: A thought on MWI and its alternative(s)

[smitra]

On 02-06-2017 02:07, Bruce Kellett wrote:

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation of our 
belonging  to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in 
Bell's

theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as in
any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. There is 
no non-locality in some mysterious sense like there is in the CI where 
somehow there is a non-local effect but you don;t have information 
transfer. The mistake most people make when arguing that the MWI 
doesn't resolve the problem is that they can't get their head around 
the fact that even when Alice and Bob meet and Alice has not yet 
communicated everything  that's necessary to Bob, that the Alice that 
Bob sees has yet to collapse in the branch corresponding to whatever 
she is going to say (Bob's consciousness is thus located in many 
different branches of Alice, even if the atoms in his body will be in 
different states due to decoherence).


I think that either you or someone else said something like this when
this was last discussed. I have a couple of points to make:

1. This is not quantum mechanics, or the many worlds interpretation of
QM. It is your own idiosyncratic theory that has no bearing on the
question of non-locality in QM.

2. Even in its own terms, this theory is nothing more than an
undisguised appeal to magic. You want consciousness to be unrelated to
the decohered body. That conflicts with the overwhelming experimental
evidence in favour of the supervenience on consciousness on the
physical brain -- they move in lockstep, so if your body has decohered
having obtained a particular measurement result, all copies (if there
be such) of this consciousness are conscious of the same measurement
result. By the identity of indiscernibles, there is then only one body
and one consciousness. That is what QM and MWI tell you, any
deviations are simple fantasy.

Bruce




Suppose Alice and Bob are robots with classical processors, the  states 
of each register can only be 0 and 1. Whatever Bob is conscious of must 
then be contained in the bitstring that specifies the state his 
processor is in. Decoherence has  no effect on that bitstring. Until 
that time that Bob asks Alice about her setting of her polarizer, Bob's 
consciousness is exactly the same across the different branches in which 
Alice gives a different answer, despite rapid decoherence.


Real human beings can be expected to fit well within this model. It is 
known that there typically is a lot of information present in the 
unconscious mind that we're not aware of. So, your consciousness could 
be identical across many branches even if your brain had split and the 
unconscious mind is already diverging.  Take e.g. experiments where you 
are making a random choice and on the basis on functional MRI scans the 
experimenters are able to predict your choice before you have even made 
up your mind.


So, this is same good old QM in the MWI where an observer's 
consciousness  is modeled as a finite state machine described by a 
finite bitstring. We can then work in the basis where the observables 
for the bits of the bitstrings are all diagonal, this then corresponds 
to the observer having a definite conscious experience.


In practice, what this means is that you can be in a macroscopic 
superposition long after decoherence has for all practical purposes made 
the superposition inaccessible to be probed using interference or other 
experiments.


For example, if a spin is polarized in the positive x-direction and the 
z-component is measured, and I'm not aware of the outcome of the result 
then my consciousness, as specified by the bitstring that contains all 
the information that I'm aware of,  cannot possibly contain the result 
of the outcome of the measurement before I'm told what the result is.


 In a sector where my consciousness is described by bitstring X after 
the spin has been measured, the state will have to be of the form:


1/sqrt(2) |X> [|up, Universe(up)> + |down, Universe(down> ]

where Universe(up)  and Universe(down) are different states of the rest 
of the universe, but my consciousness is described by X and this is not 
affected by the decoherence caused by measuring the spin. In general 
there will be a summation of such terms where X takes different values 
and Universe(up) and Universe(down) will then depend on X, however, I 
can only ever find myself in a branch were X takes some de

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 1/06/2017 10:19 pm, Bruno Marchal wrote:

On 01 Jun 2017, at 02:26, Bruce Kellett wrote:
On 1/06/2017 4:43 am, Bruno Marchal wrote:

On 31 May 2017, at 04:01, Bruce Kellett wrote:

On 30/05/2017 9:35 pm, Bruno Marchal wrote:

On 30 May 2017, at 11:28, Telmo Menezes wrote:


I get your point with decoherence.
Again, I would say that it all depends on theories of mind. What 
does
mind supervene on? Perhaps it is true that every single coupling 
with

the environment prevents the current observer state to become
compatible with other branches. But can we be sure? I feel that such
certainties come from a strong belief in emergentism (which I cannot
disprove, but find problematic).


It is impossible to recohere the past, FAPP.

But only FAPP. To make the blue T-rex interfereing with the 
red-T-rex, we must erase the trace of particle interaction between 
the T-rex in its whole light-cone, and this without forgetting the 
particles "swallowed" by the black-holes, etc. It is just 
completely impossible, but to derive from that the unicity of the 
past, is, it seems to me (and you if I understood well) is invalid.


I think the recoherence of paths that have completely decohered is 
more than just FAPP impossible, I think it is impossible in 
principle. One major problem with recoherence in general is that 
information leaks from the paths at the speed of light (as well as 
less slowly for other interactions). Since this vital information 
goes out along the light cone, it can never be recaptured and 
returned to the original interaction.


In QM + special relativity OK. (note that to me QM + special 
relativity => no collapse (and even the Many dreams, but we have 
agreed to disagree on this if I remember well).


Reasoning in QM without SR is not very profitable. Besides, QM + SR 
does not particularly imply MWI -- it is perfectly possible to have a 
consistent collapse model of QM+SR. I know you don't agree because of 
the non-locality implied by EPR, but this non-locality is not removed 
in MWI, regardless of what you might say.


I don't see it, and the mast time we discuss this, we conclude on some 
vocabulary problem. When there is no collapse, measurement tells to 
people light separated in which branch theiy belongs, but to exploits 
that information, they need to come into contact.


Last time we discussed this, no resolution was achieved. In QM, with or 
without collapse, decoherence and the transition from the pure state to 
a mixture gives a definite measurement result. Without collapse, 
different branches get different results, but once obtained, these 
results are fixed, and are not affected by whether Alice and Bob 
exchange information or not.


Consequently, indispensable phase information is lost *in 
principle*, so the recoherence is, in general, impossible.


OK. (I was reasoning in naive classical QM)

Of course, with carefully constructed systems, where the loss of 
information along the light cone is prevented, recoherence is 
possible in special circumstances, but not in general.


From this, the uniqueness of the past of any decoherent history is 
assured. So deriving the unicity (if I understand this use of the 
word) is by no means invalid -- it is proved.


In QM + SR. OK.

Even if one encounters one of those rare situations in which 
recoherence is achieved, that still does not invalidate the 
uniqueness of the past history -- recoherence, if it occurs, simply 
means that no new branches are formed at that point, so the 
decoherent history remains unique.


OK. That might suggest that we identify our indistinguishible past 
in arithmetic, if we assume mechanism. I use the Y = II principle, 
or the "quantum" linearity of the tensor product "@": we have that  
a @ (b + c) = (a @ b) + (a @ c).


That makes sense.


Linearity is the heart of QM. It is linearity that allows 
superpositions, and leads to all the "quantum weirdness".


I agree. Both "linearities" (the quantum evolution, and the tensor 
products).



...
But those state difference are accessible to the observers, and 
indeed, only this makes the analogy with step 3 working.


In MWI, the differences are not observable by anyone. Any observer 
has access to only one branch, so only one copy. They can say nothing 
about the other branch.


The difference are not observable, but are very gross, like seeing a 
cat dead, or alive. Linearity prevent any direct view of that 
difference, but it exists, when we assume QM (and non collapse).


It is not linearity that prevents macro-superpositions -- it is 
decoherence and the reduction to a mixed state. The difference between 
the measurement outcomes exists whatever interpretation of QM you impose.


...
Of course, it assures them in all branches, where indeed Aspect like 
experiences can be made. It seems to me that we did agree on this: 
that non-locality does not entail any physical influence in the 
past. That does happen in the unique universe view though; even if 

Re: A thought on MWI and its alternative(s)

[Bruce Kellett]

On 2/06/2017 7:28 am, smitra wrote:

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

Non-locality is not removed in MWI as you appear to believe.

For me the abandon of the collapse is the solution of the EPR 
"paradox", and Aspect experience is somehow the confirmation of our 
belonging  to macrosuperposition.


The non-local (paradoxical) nature of EPR remains even without
collapse. As on the previous occasion we discussed this, you were
unable to demonstrate where the notion of 'collapse' is used in Bell's
theorem - all Bell requires is that measurements give results, and
that is what the whole of physics is based on: in MWI as well as in
any other interpretation.

Bruce


In the MWI there are only trivial common cause like effects. There is 
no non-locality in some mysterious sense like there is in the CI where 
somehow there is a non-local effect but you don;t have information 
transfer. The mistake most people make when arguing that the MWI 
doesn't resolve the problem is that they can't get their head around 
the fact that even when Alice and Bob meet and Alice has not yet 
communicated everything  that's necessary to Bob, that the Alice that 
Bob sees has yet to collapse in the branch corresponding to whatever 
she is going to say (Bob's consciousness is thus located in many 
different branches of Alice, even if the atoms in his body will be in 
different states due to decoherence).


I think that either you or someone else said something like this when 
this was last discussed. I have a couple of points to make:


1. This is not quantum mechanics, or the many worlds interpretation of 
QM. It is your own idiosyncratic theory that has no bearing on the 
question of non-locality in QM.


2. Even in its own terms, this theory is nothing more than an 
undisguised appeal to magic. You want consciousness to be unrelated to 
the decohered body. That conflicts with the overwhelming experimental 
evidence in favour of the supervenience on consciousness on the physical 
brain -- they move in lockstep, so if your body has decohered having 
obtained a particular measurement result, all copies (if there be such) 
of this consciousness are conscious of the same measurement result. By 
the identity of indiscernibles, there is then only one body and one 
consciousness. That is what QM and MWI tell you, any deviations are 
simple fantasy.


Bruce


The apparent non-locality is then purely an artifact on making such 
assumptions about localization in branches when that's wrong to do.


Saibal



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Re: A thought on MWI and its alternative(s)

[smitra]

On 01-06-2017 02:26, Bruce Kellett wrote:

On 1/06/2017 4:43 am, Bruno Marchal wrote:

On 31 May 2017, at 04:01, Bruce Kellett wrote:

On 30/05/2017 9:35 pm, Bruno Marchal wrote:

On 30 May 2017, at 11:28, Telmo Menezes wrote:


I get your point with decoherence.
Again, I would say that it all depends on theories of mind. What 
does
mind supervene on? Perhaps it is true that every single coupling 
with

the environment prevents the current observer state to become
compatible with other branches. But can we be sure? I feel that 
such
certainties come from a strong belief in emergentism (which I 
cannot

disprove, but find problematic).


It is impossible to recohere the past, FAPP.

But only FAPP. To make the blue T-rex interfereing with the 
red-T-rex, we must erase the trace of particle interaction between 
the T-rex in its whole light-cone, and this without forgetting the 
particles "swallowed" by the black-holes, etc. It is just completely 
impossible, but to derive from that the unicity of the past, is, it 
seems to me (and you if I understood well) is invalid.


I think the recoherence of paths that have completely decohered is 
more than just FAPP impossible, I think it is impossible in 
principle. One major problem with recoherence in general is that 
information leaks from the paths at the speed of light (as well as 
less slowly for other interactions). Since this vital information 
goes out along the light cone, it can never be recaptured and 
returned to the original interaction.


In QM + special relativity OK. (note that to me QM + special 
relativity => no collapse (and even the Many dreams, but we have 
agreed to disagree on this if I remember well).


Reasoning in QM without SR is not very profitable. Besides, QM + SR
does not particularly imply MWI -- it is perfectly possible to have a
consistent collapse model of QM+SR. I know you don't agree because of
the non-locality implied by EPR, but this non-locality is not removed
in MWI, regardless of what you might say.

Consequently, indispensable phase information is lost *in principle*, 
so the recoherence is, in general, impossible.


OK. (I was reasoning in naive classical QM)

Of course, with carefully constructed systems, where the loss of 
information along the light cone is prevented, recoherence is 
possible in special circumstances, but not in general.


From this, the uniqueness of the past of any decoherent history is 
assured. So deriving the unicity (if I understand this use of the 
word) is by no means invalid -- it is proved.


In QM + SR. OK.

Even if one encounters one of those rare situations in which 
recoherence is achieved, that still does not invalidate the 
uniqueness of the past history -- recoherence, if it occurs, simply 
means that no new branches are formed at that point, so the 
decoherent history remains unique.


OK. That might suggest that we identify our indistinguishible past in 
arithmetic, if we assume mechanism. I use the Y = II principle, or the 
"quantum" linearity of the tensor product "@": we have that  a @ (b + 
c) = (a @ b) + (a @ c).


That makes sense.


Linearity is the heart of QM. It is linearity that allows
superpositions, and leads to all the "quantum weirdness".




FWIW, you
are expressing my own understanding of the situation: there can be 
no
superposition of red and green screens or dinosaurs, or dead and 
live cats,
because there can be no quantum superposition of macroscopic 
objects.
Superpositions of wave functions are only possible for systems 
isolated from
interaction with their environment, which is why quantum computers 
are so
fricking hard to make: keeping aggregates of particles isolated 
from
interactions with the surrounding environment is exponentially 
more

difficult as the system grows in size.


The main question for me is this: can two branches hold different
observer states, if they differ only by things that are not
observable?


I would say no, intuitively. I would even say "no" just for the 
things not observed, even when observable.


I previously answered Telmo's question in the affirmative, viz., two 
fully decohered branches will hold different observer states, even if 
the differences are not observed or observable. So if some trivial 
physical event happens to your body, such as the decay of a K 40 
nucleus in your foot, this would not be noticeable, or even 
particularly observable even if you were looking for it. But such an 
event causes at least two branches to form every instant -- one in 
which the decay has occurred, and one in which it has not. And since 
this is a beta decay, a neutrino is lost along the light cone in 
every case of decay. Perfect recombination of the branches is, then, 
according to the above argument, not possible. You might object that 
this decay in my toe did not alter my conscious state -- that is 
correct, but there are now two copies of the Moscow man as in step 3,


My mistake here - I misremembered step 3.  Moscow is a targe

Re: A thought on MWI and its alternative(s)

[David Nyman]

On 1 June 2017 at 02:59, Bruce Kellett  wrote:

> On 1/06/2017 6:28 am, David Nyman wrote:
>
> On 31 May 2017 at 04:55, Bruce Kellett < 
> bhkell...@optusnet.com.au> wrote:
>
>> On 31/05/2017 12:30 pm, Pierz wrote:
>>
>> Thanks for these clarifications Bruce. I find your explanations to be
>> very lucid and helpful - they also confirm my own understanding.
>>
>>
>> Thank you for the kind comments, I try my best to be clear.
>>
>> IIRC, you weren't a particular fan of MWI when I last conversed with you
>> on this list.
>>
>>
>> That is indeed the case. I have several reasons to be dubious about MWI.
>> Firstly, it amounts to reifying a complex valued function that resides in
>> configuration space -- I am not sure that this is a well-defined procedure.
>> Secondly, MWI doesn't really do what it claims to do, which is to provide a
>> resolution of the measurement problem in QM. MWI doesn't provide any
>> explanation of the transition from a pure state to the mixed state that is
>> required for experiments to give definite results. At the crucial point,
>> MWI simply says "then a miracle happens!" To be more explicit,
>> deterministic evolution of the wave function by the Schrödinger equation
>> gives a full account of decoherence, and the dissemination of the coherence
>> phases into the environment. This reduces the off-diagonal elements of the
>> density matrix so that the diagonal elements become *almost* orthogonal,
>> but unitary evolution can't go the whole way. The only way one can reduce
>> the pure state to a mixture is to trace over the environmental degrees of
>> freedom, which is to say that the residual phase information is simply
>> thrown away. This trace operation is non-unitary, and there is no warrant
>> for it in the SE itself, so it is, in the final analysis, just an appeal to
>> magic.
>>
>
> Bruce, is it perhaps finally an appeal to observation per se? IOW what you
> say is of course objectively the case, but perhaps in some way the
> ​residual phase information isn't relevant (i.e. can be 'traced over') in
> the synthesis of the 'observer-observation' relation. If so, this relation
> could perhaps resolve the 'eternalist' pure state (which after all
> continues simply to be 'there' in the MWI conception) subjectively into
> what would give the 'instrumental' appearance, in effect, of the
> probability density characteristic of a mixture?
>
>
> It is often argued that the density matrix is diagonalized FAPP, and FAPP
> is all that is required. Unfortunately, I don't think that that really
> works. Even though the individual off-diagonal elements might be
> arbitrarily small, there are a very large number of them (increasing as
> further environmental degrees of freedom are included). The end result is
> that the original superposition is still intact and no 'split' has in fact
> occurred -- the situation is still completely reversible. The problem I
> point to is that there is nothing in the unitary mathematics corresponding
> to "ignoring inessential degrees of freedom". That is what the partial
> trace does, but that has to be imposed by hand, it is not automatic, and
> suffers from all the old difficulties of the Heisenberg cut -- it is
> arbitrary.
>

​It's certainly arbitrary in any objective sense, but could that still be
said under the observational assumptions I outlined? What I mean is that,
in an eternalist framework, transition from pure to mixed state might be
considered an emergent phenomenon relativised to some embedded
'point-of-view-of-interest'. So if what you term above "inessential degrees
of freedom" did indeed turn out to be inessential to "some fundamental
compositional principle of observer-hood" we could perhaps restore from
this the operational aspect of an apparently mixed state whilst the pure
state continued to be the case in the idealised eternalist frame. In such a
case the sense of arbitrariness you mention above might be alleviated.


>
> Then there wouldn't seem to me to be a necessary idea of 'collapse'
> involved, except in a purely epistemological sense. The term 'subjective'
> here is more in the sense of some fundamental compositional principle of
> observer-hood than a restriction to out-and-out 'waking consciousness'. I'm
> not sure if this has any necessary connection  to Lockwood's idea of a
> 'consciousness basis'. Of course quite clearly any of this would be highly
> speculative, but I'm wondering if it could make any sense in principle? I'd
> value your opinion.
>
>
> I think that something like this was what Everett had in mind when called
> this idea the "relative state model". I think he saw the observer as
> complete in every branch, so that
>
>  |psi> = (|1> + \2>)|me>|environment> --> (|1>|me_1> +
> |2>|me_2>)|environment>
>   --> |1>|me_1>|environment_1> + |2>|me_2>|environment_2>
>
> and he then considered the two parts of the development to be complete in
> themselves, so we found ourselves in one or the other branch.

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 01 Jun 2017, at 13:02, Bruce Kellett wrote:


On 1/06/2017 8:21 pm, Bruno Marchal wrote:

On 31 May 2017, at 09:15, Bruce Kellett wrote:

On 31/05/2017 4:40 pm, Pierz wrote:


>> On 5/30/2017 7:30 PM, Pierz wrote:
>>> Thanks for these clarifications Bruce. I find your  
explanations to be very lucid and helpful - they also confirm my  
own understanding. IIRC, you weren't a particular fan of MWI when  
I last conversed with you on this list. I wonder if you'd care to  
comment on my original argument on this thread - which has of  
course now been swamped by the usual brawls. Does not a single  
history + the physical insignificance of the notion of a current  
moment mean that there is also only a single possible future?
>> I don't see how that follows.  In the usual model of forking  
in the future direction every current moment has a single  
history, but multiple futures.


Multiple futures = MWI, surely.


Not necessarily. If you insist on Schrödinger determinism, then  
yes, by reification of the wave function. But if the wave function  
is only epistemological, then there is only one probabilistic  
future.


How could an epistemological wave interfere all by itself? It seems  
simpler to say that the wave is real, but that the local, one  
branch, perception is epistemological.


I think you misunderstand this use of the word "epistemological".  
When it is said that the wave function is merely epistemological,  
what is meant that it is merely a calculational device: the wave  
function encapsulates our knowledge of the system of interest, and  
tells us how to calculate the probabilities of various outcomes. In  
other words, it is not a 'real' wave in space-time.


Yes. That is the problem. How a non real wave in space time can  
interfere really in space-time? Of course, the answer is simple with  
the MWI, but asks for real infuence at a distance with the Mono-world  
assumption.







When I say a single history, I mean that from the Big Bang  
forward, the universe only followed one branch.


And that can lead into the future, only one probabilistic future.


>>
>>> And if the future is predetermined in this way, isn't this a  
serious issue for single universe models of QM? How can the  
outcome of quantum events be both inevitable and random?
>> Having a single future isn't the same as being determined.  A  
single future in which situation A is sometimes followed by B and  
sometimes by C is still random.


It depends on perspective. It's true that from 1p, it looks  
random. But from 3p, it is static and always the same, and in  
this sense determined.


Not true, the 3p view of the future is still just a single  
probabilistic world line. It is only the bird view, from outside  
space and time, that gives the appearance that there are multiply  
existing futures. Neither we from the 1p perspective, or from  
outside ourselves in the 3p perspective, can we ever see any of  
the other branches predicted by MWI.


Yes, like in WM-duplication.


No, that is a serious mistake. Unitary evolution of the wave  
function is not at all like the person duplication experiments. The  
main difference is that the duplicates of the Helsinki man are never  
in a pure quantum state.


That was not the point. The comparison is on the reasult measurement,  
not on the reason of the parallel states. With mechanism, the reason  
are the same (the first person indeterminacy). With collapse, we need  
magic.



The teleportation to W or M is of separate classical entities, There  
is no superposition principle for duplicated persons.


You can defined for the Helsinki guy. He is in a sort of (non quantum)  
superposition state in helsinki, which indeed, like in the MWI, is  
just his ignoance on which computations he belongs. I use Y = II, if  
that is still needed to say.







The guy in Helsinki can predict that his first person future will  
be unique, even if he knows that in the "bird" picture, that  
outside the teleportation/duplication boxes, there will be two  
versions of him.


That is not the "bird" picture, that is merely the objective 3p  
picture of the ordinary classical world. The bird picture is solely  
to do with the pure state that is preserved in the unitary evolution  
pure state of the wave function.


I do not assume QM in that context. I was just doing an anlogy, at  
this stage.






This is where the problems with MWI really show up. When you have a  
quantum event with, say, two possible outcomes with equal  
probabilities, such as measuring the polarization of an unpolarized  
photon, the initial probability is 0.5 for each polarization. But  
after the measurement, the probability for the observed result  
(horizontal or transverse as observed) is unity -- because the  
result has been observed, it is now certain. So how did the  
probability suddenly change from 0.5 to 1.0?


Well, with the MWI, it is the same as the dropping from the Helsinki  
1/2, to the W(M) "local

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 01 Jun 2017, at 03:59, Bruce Kellett wrote:


On 1/06/2017 6:28 am, David Nyman wrote:
On 31 May 2017 at 04:55, Bruce Kellett   
wrote:

On 31/05/2017 12:30 pm, Pierz wrote:
Thanks for these clarifications Bruce. I find your explanations to  
be very lucid and helpful - they also confirm my own understanding.


Thank you for the kind comments, I try my best to be clear.

IIRC, you weren't a particular fan of MWI when I last conversed  
with you on this list.


That is indeed the case. I have several reasons to be dubious about  
MWI. Firstly, it amounts to reifying a complex valued function that  
resides in configuration space -- I am not sure that this is a well- 
defined procedure. Secondly, MWI doesn't really do what it claims  
to do, which is to provide a resolution of the measurement problem  
in QM. MWI doesn't provide any explanation of the transition from a  
pure state to the mixed state that is required for experiments to  
give definite results. At the crucial point, MWI simply says "then  
a miracle happens!" To be more explicit, deterministic evolution of  
the wave function by the Schrödinger equation gives a full account  
of decoherence, and the dissemination of the coherence phases into  
the environment. This reduces the off-diagonal elements of the  
density matrix so that the diagonal elements become *almost*  
orthogonal, but unitary evolution can't go the whole way. The only  
way one can reduce the pure state to a mixture is to trace over the  
environmental degrees of freedom, which is to say that the residual  
phase information is simply thrown away. This trace operation is  
non-unitary, and there is no warrant for it in the SE itself, so it  
is, in the final analysis, just an appeal to magic.


Bruce, is it perhaps finally an appeal to observation per se? IOW  
what you say is of course objectively the case, but perhaps in some  
way the ​residual phase information isn't relevant (i.e. can be  
'traced over') in the synthesis of the 'observer-observation'  
relation. If so, this relation could perhaps resolve the  
'eternalist' pure state (which after all continues simply to be  
'there' in the MWI conception) subjectively into what would give  
the 'instrumental' appearance, in effect, of the probability  
density characteristic of a mixture?


It is often argued that the density matrix is diagonalized FAPP, and  
FAPP is all that is required. Unfortunately, I don't think that that  
really works. Even though the individual off-diagonal elements might  
be arbitrarily small, there are a very large number of them  
(increasing as further environmental degrees of freedom are  
included). The end result is that the original superposition is  
still intact and no 'split' has in fact occurred -- the situation is  
still completely reversible. The problem I point to is that there is  
nothing in the unitary mathematics corresponding to "ignoring  
inessential degrees of freedom". That is what the partial trace  
does, but that has to be imposed by hand, it is not automatic, and  
suffers from all the old difficulties of the Heisenberg cut -- it is  
arbitrary.


Then there wouldn't seem to me to be a necessary idea of 'collapse'  
involved, except in a purely epistemological sense. The term  
'subjective' here is more in the sense of some fundamental  
compositional principle of observer-hood than a restriction to out- 
and-out 'waking consciousness'. I'm not sure if this has any  
necessary connection  to Lockwood's idea of a 'consciousness  
basis'. Of course quite clearly any of this would be highly  
speculative, but I'm wondering if it could make any sense in  
principle? I'd value your opinion.


I think that something like this was what Everett had in mind when  
called this idea the "relative state model". I think he saw the  
observer as complete in every branch, so that


 |psi> = (|1> + \2>)|me>|environment> --> (|1>|me_1> + |2>| 
me_2>)|environment>

  --> |1>|me_1>|environment_1> + |2>|me_2>|environment_2>

and he then considered the two parts of the development to be  
complete in themselves, so we found ourselves in one or the other  
branch. Everett had no particular commitment to the existence of the  
other branches --


Well Everett denied this, and his son, and daughter confirmed this, as  
I have read in a short biography. Everett told that he had been asked  
to withdraw any tlak on parallel world, and the term relative states  
was proposed by the editor of the journal (Review of Modern Physics).  
This seems also clear from his long text.




it was DeWitt who developed the idea of many worlds. The trouble  
here, as is well known, is that the above is still a pure state, and  
we require a reduction to a mixed state in order to be able to  
consider one or other branch on its own. The 'collapse' can be  
regarded as epistemological, but we will still need the mixed state.


OK with this.






Thirdly, the non-observed branches in MWI 

Re: A thought on MWI and its alternative(s)

[Bruno Marchal]

On 01 Jun 2017, at 02:26, Bruce Kellett wrote:


On 1/06/2017 4:43 am, Bruno Marchal wrote:

On 31 May 2017, at 04:01, Bruce Kellett wrote:

On 30/05/2017 9:35 pm, Bruno Marchal wrote:

On 30 May 2017, at 11:28, Telmo Menezes wrote:


I get your point with decoherence.
Again, I would say that it all depends on theories of mind. What  
does
mind supervene on? Perhaps it is true that every single coupling  
with

the environment prevents the current observer state to become
compatible with other branches. But can we be sure? I feel that  
such
certainties come from a strong belief in emergentism (which I  
cannot

disprove, but find problematic).


It is impossible to recohere the past, FAPP.

But only FAPP. To make the blue T-rex interfereing with the red-T- 
rex, we must erase the trace of particle interaction between the  
T-rex in its whole light-cone, and this without forgetting the  
particles "swallowed" by the black-holes, etc. It is just  
completely impossible, but to derive from that the unicity of the  
past, is, it seems to me (and you if I understood well) is invalid.


I think the recoherence of paths that have completely decohered is  
more than just FAPP impossible, I think it is impossible in  
principle. One major problem with recoherence in general is that  
information leaks from the paths at the speed of light (as well as  
less slowly for other interactions). Since this vital information  
goes out along the light cone, it can never be recaptured and  
returned to the original interaction.


In QM + special relativity OK. (note that to me QM + special  
relativity => no collapse (and even the Many dreams, but we have  
agreed to disagree on this if I remember well).


Reasoning in QM without SR is not very profitable. Besides, QM + SR  
does not particularly imply MWI -- it is perfectly possible to have  
a consistent collapse model of QM+SR. I know you don't agree because  
of the non-locality implied by EPR, but this non-locality is not  
removed in MWI, regardless of what you might say.


I don't see it, and the mast time we discuss this, we conclude on some  
vocabulary problem. When there is no collapse, measurement tells to  
people light separated in which branch theiy belongs, but to exploits  
that information, they need to come into contact.







Consequently, indispensable phase information is lost *in  
principle*, so the recoherence is, in general, impossible.


OK. (I was reasoning in naive classical QM)

Of course, with carefully constructed systems, where the loss of  
information along the light cone is prevented, recoherence is  
possible in special circumstances, but not in general.


From this, the uniqueness of the past of any decoherent history is  
assured. So deriving the unicity (if I understand this use of the  
word) is by no means invalid -- it is proved.


In QM + SR. OK.

Even if one encounters one of those rare situations in which  
recoherence is achieved, that still does not invalidate the  
uniqueness of the past history -- recoherence, if it occurs,  
simply means that no new branches are formed at that point, so the  
decoherent history remains unique.


OK. That might suggest that we identify our indistinguishible past  
in arithmetic, if we assume mechanism. I use the Y = II principle,  
or the "quantum" linearity of the tensor product "@": we have that   
a @ (b + c) = (a @ b) + (a @ c).


That makes sense.


Linearity is the heart of QM. It is linearity that allows  
superpositions, and leads to all the "quantum weirdness".


I agree. Both "linearities" (the quantum evolution, and the tensor  
products).









FWIW, you
are expressing my own understanding of the situation: there can  
be no
superposition of red and green screens or dinosaurs, or dead  
and live cats,
because there can be no quantum superposition of macroscopic  
objects.
Superpositions of wave functions are only possible for systems  
isolated from
interaction with their environment, which is why quantum  
computers are so
fricking hard to make: keeping aggregates of particles isolated  
from
interactions with the surrounding environment is exponentially  
more

difficult as the system grows in size.


The main question for me is this: can two branches hold different
observer states, if they differ only by things that are not
observable?


I would say no, intuitively. I would even say "no" just for the  
things not observed, even when observable.


I previously answered Telmo's question in the affirmative, viz.,  
two fully decohered branches will hold different observer states,  
even if the differences are not observed or observable. So if some  
trivial physical event happens to your body, such as the decay of  
a K 40 nucleus in your foot, this would not be noticeable, or even  
particularly observable even if you were looking for it. But such  
an event causes at least two branches to form every instant -- one  
in which the decay has occurred, and one in which it has