date:20191015

On Tuesday, October 15, 2019 at 5:29:21 PM UTC-5, Philip Thrift wrote:
>
>
>
> On Tuesday, October 15, 2019 at 4:14:39 PM UTC-5, John Clark wrote:
>>
>> On Tue, Oct 15, 2019 at 1:50 PM 'Brent Meeker'  <
>> everyth...@googlegroups.com> wrote:
>>
>>>
>> * > Curiously, Deutsch used a quantum computer in a thought experiment to 
>>> prove multiple worlds.*
>>
>>
>> He did indeed, I read about it 30 years ago in Deutsch's book "The Ghost 
>> In The Atom" and that was when I started to take the MWI seriously. 
>> Deutsch's test would be very difficult to perform but the reason it's so 
>> difficult is not the Many World's fault, the reason is that the 
>> conventional view says conscious observers obey different laws of physics, 
>> Many Worlds says they do not, so to test who's right we need a mind that 
>> uses quantum properties. Quantum Computers have advanced enormously over 
>> the last 30 years so I wouldn't be surprised if it or something very much 
>> like it is actually performed in a decade or two.
>>
>> An intelligent quantum computer shoots photons at a metal plate one at a 
>> time that has 2 small slits in it, and then the photons hit a photographic 
>> plate. Nobody looks at the photographic plate till the very end of the 
>> experiment. The quantum mind has detectors near each slit so it knows which 
>> slit the various photons went through. After each photon passes the slits 
>> but before they hit the photographic plate the quantum mind signs a 
>> document saying that it has observed each and every photon and knows which 
>> slit each photon went through. It is very important that the document does 
>> NOT say which slit any photon went through, it only says that they went 
>> through one slit and only one slit  and the mind has knowledge of which 
>> one. There is a signed document to this effect for every photon it shoots.
>>
>> Now the mind uses quantum erasure to completely destroy its memory of 
>> which slit any of the photons went through; the only part remaining in the 
>> universe is the document which states that each photon went through one and 
>> only one slit and the mind (at the time) knew which one. Now develop the 
>> photographic plate and look at it. If you see interference bands then the 
>> Many World interpretation is correct. If you do not see interference bands 
>> then there are no worlds but this one and the conventional quantum 
>> interpretation is correct.
>>
>> This works because in the Copenhagen interpretation when the results of a 
>> measurement enters the consciousness of an observer the wave function 
>> collapses, in effect all the universes except one disappear without a trace 
>> so you get no interference. In the Many Worlds model all the other worlds 
>> will converge back into one universe because information on which slit the 
>> various photons went through was the only thing that made one universe 
>> different from another, so when that was erased they became identical again 
>> and merged, but their influence will still be felt, you'll see ambiguous 
>> evidence that the photon went through slot A only and ambiguous evidence it 
>> went through slot B only, and that's what causes the interference pattern.
>>
>> John K Clark
>>
>
>
> But the path integral is both interpretation of quantum computing - 
> https://arxiv.org/abs/quant-ph/0607151 (2006) - and algorithm for the 
> Google quantum computer simulator - https://arxiv.org/abs/1807.10749 
> (2018). The Google quantum computer paper does not mention "many worlds".
>
> @philipthrift 
>

No it is not. I have worked a derivation of a path integral here before. If 
I have to I will do it again. There is nothing in a path integral outside 
of plain vanilla QM or QFT. Dowker and others start to assign ontological 
meaning to paths and the rest and launch into interpretation.

LC 

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Re: Something deeply hidden in the forest

2019-10-15 Thread John Clark

On Tue, Oct 15, 2019 at 6:01 PM 'Brent Meeker'  <
everything-list@googlegroups.com> wrote:

> >> Oh for christ sake! As I've said over and over, in Many Worlds a
>> change, any change, is equivalent to a measurement and it doesn't make the
>> slightest difference if that change involves consciousness or not. If Brent
>> Meeker flips a coin and it comes out heads then obviously that Brent Meeker
>> is not living in the world where it came out tails
>
> > Any change??
>

Yes any change, and if you don't like it don't complain to me complain to
Schrodinger's Equation.

> * > What about the world in which a K40 atom in JKC's blood stream decayed
> compared to one in which it didn't?*
>

What about it?

>
> * > What about the one were this N2 molecule bounced left instead of right
> on colliding with that CO2 molecule?*
>

I repeat, what about it?

*> Well in practice he has to measure them in an orthogonal basis in order
> to erase the welcher weg.*

I don't quite see how but apparently you think that will result in there
being a difference between the two universes and thus you predict no
interference pattern will be seen when the photographic plate is developed,
but David Deutsch thinks bands of interference will be on that plate. I'm
not certain who is right but I'd give 2 to 1 odds that it's Deutsch. Well
know for sure before 2050, maybe much sooner.

John K Clark

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Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 4:14:39 PM UTC-5, John Clark wrote:
>
> On Tue, Oct 15, 2019 at 1:50 PM 'Brent Meeker'  <
> everyth...@googlegroups.com > wrote:
>
>>
> * > Curiously, Deutsch used a quantum computer in a thought experiment to 
>> prove multiple worlds.*
>
>
> He did indeed, I read about it 30 years ago in Deutsch's book "The Ghost 
> In The Atom" and that was when I started to take the MWI seriously. 
> Deutsch's test would be very difficult to perform but the reason it's so 
> difficult is not the Many World's fault, the reason is that the 
> conventional view says conscious observers obey different laws of physics, 
> Many Worlds says they do not, so to test who's right we need a mind that 
> uses quantum properties. Quantum Computers have advanced enormously over 
> the last 30 years so I wouldn't be surprised if it or something very much 
> like it is actually performed in a decade or two.
>
> An intelligent quantum computer shoots photons at a metal plate one at a 
> time that has 2 small slits in it, and then the photons hit a photographic 
> plate. Nobody looks at the photographic plate till the very end of the 
> experiment. The quantum mind has detectors near each slit so it knows which 
> slit the various photons went through. After each photon passes the slits 
> but before they hit the photographic plate the quantum mind signs a 
> document saying that it has observed each and every photon and knows which 
> slit each photon went through. It is very important that the document does 
> NOT say which slit any photon went through, it only says that they went 
> through one slit and only one slit  and the mind has knowledge of which 
> one. There is a signed document to this effect for every photon it shoots.
>
> Now the mind uses quantum erasure to completely destroy its memory of 
> which slit any of the photons went through; the only part remaining in the 
> universe is the document which states that each photon went through one and 
> only one slit and the mind (at the time) knew which one. Now develop the 
> photographic plate and look at it. If you see interference bands then the 
> Many World interpretation is correct. If you do not see interference bands 
> then there are no worlds but this one and the conventional quantum 
> interpretation is correct.
>
> This works because in the Copenhagen interpretation when the results of a 
> measurement enters the consciousness of an observer the wave function 
> collapses, in effect all the universes except one disappear without a trace 
> so you get no interference. In the Many Worlds model all the other worlds 
> will converge back into one universe because information on which slit the 
> various photons went through was the only thing that made one universe 
> different from another, so when that was erased they became identical again 
> and merged, but their influence will still be felt, you'll see ambiguous 
> evidence that the photon went through slot A only and ambiguous evidence it 
> went through slot B only, and that's what causes the interference pattern.
>
> John K Clark
>


But the path integral is both interpretation of quantum computing - 
https://arxiv.org/abs/quant-ph/0607151 (2006) - and algorithm for the 
Google quantum computer simulator - https://arxiv.org/abs/1807.10749 
(2018). The Google quantum computer paper does not mention "many worlds".

@philipthrift 

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Path integrals for the brain



*Path Integrals of Information*
http://www.cs.yale.edu/publications/techreports/tr1226.pdf

*Probabilistic tractography, Path Integrals and the Fokker Planck equation*
https://arxiv.org/pdf/1502.06793.pdf

*Path Integral Approach to Random Neural Networks*
https://arxiv.org/pdf/1809.06042.pdf

cf. *A proposed mechanism for mind-brain interaction using extended Bohmian 
quantum mechanics*
https://www.ncbi.nlm.nih.gov/pubmed/31388577


@philipthrift

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Re: Something deeply hidden in the forest

2019-10-15 Thread 'Brent Meeker' via Everything List

On 10/15/2019 1:46 PM, John Clark wrote:
On Mon, Oct 14, 2019 at 6:22 PM 'Brent Meeker'
> wrote:

>>This is physics not mathematics, the Born rule isn't derived
it's observed, and it's observed to work.

/> But then MWI can't claim to be simpler and "purer" than CI. /

CI says the laws of physics work one way if a system is not observed
and another way if it is observed, and it never makes clear what
observed means. The MWI says the laws of physics only work one way and
it makes crystal clear what observed means. And I don't know about
purer but MWI is certainly simpler than interpretations that are
compelled to add extra terms to Schrodinger's Equation that, other
than get rid of other worlds, do nothing but complicate a already
hideously complicated calculation.

>> I like Many Worlds because it gives me a little intuitive
understanding why we can only make probabilistic predictions
even though the underlying mathematics is completely
deterministic, and I like it because it gives a precise
definition of "measurement".

/> That your consciousness becomes correlated with an eigenvalue
of some Hermitean operator?/

No.

> Does MWI define when a measurement has taken place or not?

It does.

> /What is this precise definition of which you write? /

Oh for christ sake! As I've said over and over, in Many Worlds a
change, any change, is equivalent to a measurement and it doesn't make
the slightest difference if that change involves consciousness or not.
If Brent Meeker flips a coin and it comes out heads then obviously
that Brent Meeker is not living in the world where it came out tails.

Any change?? What about the world in which a K40 atom in JKC's blood
stream decayed compared to one in which it didn't? What about the one
were this N2 molecule bounced left instead of right on colliding with
that CO2 molecule?

In the same way if you do the two slit experiment and the photon goes
through slit A then you are not living in the world where it went
through slot B, but the 2 slit experiment can be a little different from

the simple coin toss example.

If after the photon makes its decision on which of the 2 slits to go
through it then hits a photographic plate then both photons in both
universes are destroyed and thus there is no longer any difference
between the two, so the universes will merge back together. So in that
newly re-merged universe there will be ambiguity about which slit the
photon actually went through which is why that photon will contribute
to the interference pattern that shows up on the photographic plate.
The important thing is that the photographic plate destroys the photon
in both universes so you could replace the plate with a brick wall and
the same thing would happen, it would just be harder to tell that
something funny was going on.

However if you had a detector next to each slit and sent information
on which slit the photon went through to your computer then there
would still be a physical difference between universes even though the
photon no longer exists in either, one universe would have computer in
it with a few magnetic spots on its disk drive indicating the photon
went through slot A but in the other universe the magnetic spots would
be in a slightly different place indicating slot B, so the universes
remain different, so they don't remerge, so there is no ambiguity in
either universe, so neither universe will see a interference pattern.

Universes don't usually merge back together because the differences
between them usually accelerates so it's astronomically unlikely they
will ever become identical again, however a skilled experimenter can
make the change to be very small and then can gently nudge them back
together.

Well in practice he has to measure them in an orthogonal basis in order
to erase the welcher weg.

Brent

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 universes,
and you, will split and never recombine, and so of course you will see
no interference effect. The beautiful part of the theory is that it
doesn't have to explain what an observer is and that's why a brick
wall will work just as well as a photographic plate.

John K Clark
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Re: Something deeply hidden in the forest

2019-10-15 Thread Bruce Kellett

On Wed, Oct 16, 2019 at 7:47 AM John Clark  wrote:

>
> Oh for christ sake! As I've said over and over, in Many Worlds a change,
> any change, is equivalent to a measurement and it doesn't make the
> slightest difference if that change involves consciousness or not. If Brent
> Meeker flips a coin and it comes out heads then obviously that Brent Meeker
> is not living in the world where it came out tails. In the same way if you
> do the two slit experiment and the photon goes through slit A then you are
> not living in the world where it went through slot B, but the 2 slit
> experiment can be a little different from
> the simple coin toss example.
>
> If after the photon makes its decision on which of the 2 slits to go
> through it then hits a photographic plate then both photons in both
> universes are destroyed and thus there is no longer any difference between
> the two, so the universes will merge back together. So in that newly
> re-merged universe there will be ambiguity about which slit the photon
> actually went through which is why that photon will contribute to  the
> interference pattern that shows up on the photographic plate. The important
> thing is that the photographic plate destroys the photon in both universes
> so you could replace the plate with a brick wall and the same thing would
> happen, it would just be harder to tell that something funny was going on.
>
> However if you had a detector next to each slit and sent information on
> which slit the photon went through to your computer then there would still
> be a physical difference between universes even though the photon no longer
> exists in either, one universe would have computer in it with a few
> magnetic spots on its disk drive indicating the photon went through slot A
> but in the other universe the magnetic spots would be in a slightly
> different place indicating slot B, so the universes remain different, so
> they don't remerge, so there is no ambiguity in either universe, so neither
> universe will see a interference pattern.
>
> Universes don't usually merge back together because the differences
> between them usually accelerates so it's astronomically unlikely they will
> ever become identical again, however a skilled experimenter can make the
> change to be very small and then can gently nudge them back together.  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 universes, and you,
> will split and never recombine, and so of course you will see no
> interference effect. The beautiful part of the theory is that it doesn't
> have to explain what an observer is and that's why a brick wall will work
> just as well as a photographic plate.
>

I think an equivalent experiment has been done. It is the quantum eraser
work of Zeilinger and associates:

https://en.wikipedia.org/wiki/Quantum_eraser_experiment

This also illustrates delayed choice, since the decision to erase the
"welcher weg"  information can be made after the photons have been recorded
on the screen. Ingenious variations of this have been done using polarised
photons as carriers of the "which way" information, using rotated
polarisers to erase the information or not.

I don't think anyone has seen many worlds emerge from these experiments.
They have straightforward interpretation in any quantum interpretation.

Bruce

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Re: Something deeply hidden in the forest

2019-10-15 Thread 'Brent Meeker' via Everything List

On 10/15/2019 2:14 PM, John Clark wrote:
On Tue, Oct 15, 2019 at 1:50 PM 'Brent Meeker'
> wrote:

/> Curiously, Deutsch used a quantum computer in a thought
experiment to prove multiple worlds./

He did indeed, I read about it 30 years ago in Deutsch's book "The
Ghost In The Atom" and that was when I started to take the MWI
seriously. Deutsch's test would be very difficult to perform but the
reason it's so difficult is not the Many World's fault, the reason is
that the conventional view says conscious observers obey different
laws of physics, Many Worlds says they do not, so to test who's right
we need a mind that uses quantum properties. Quantum Computers have
advanced enormously over the last 30 years so I wouldn't be surprised
if it or something very much like it is actually performed in a decade
or two.

An intelligent quantum computer shoots photons at a metal plate one at
a time that has 2 small slits in it, and then the photons hit a
photographic plate. Nobody looks at the photographic plate till the
very end of the experiment. The quantum mind has detectors near each
slit so it knows which slit the various photons went through. After
each photon passes the slits but before they hit the photographic
plate the quantum mind signs a document saying that it has observed
each and every photon and knows which slit each photon went through.
It is very important that the document does NOT say which slit any
photon went through, it only says that they went through one slit and
only one slit and the mind has knowledge of which one. There is a
signed document to this effect for every photon it shoots.

Now the mind uses quantum erasure to completely destroy its memory of
which slit any of the photons went through; the only part remaining in
the universe is the document which states that each photon went
through one and only one slit and the mind (at the time) knew which
one. Now develop the photographic plate and look at it. If you see
interference bands then the Many World interpretation is correct.

But as Scott Aaronson noted the interference had to happen in one world.

If you do not see interference bands then there are no worlds but this
one and the conventional quantum interpretation is correct.

This works because in the Copenhagen interpretation when the results
of a measurement enters the consciousness of an observer the wave
function collapses,

That was von Neumann's (and briefly Wigner's) interpretation, but Bohr,
Heisenberg, and others always held that any macroscopic instrument would
collapse the wf. The development of decoherence theory has made that
more well defined.

Brent

in effect all the universes except one disappear without a trace so
you get no interference. In the Many Worlds model all the other worlds
will converge back into one universe because information on which slit
the various photons went through was the only thing that made one
universe different from another, so when that was erased they became
identical again and merged, but their influence will still be felt,
you'll see ambiguous evidence that the photon went through slot A only
and ambiguous evidence it went through slot B only, and that's what
causes the interference pattern.

John K Clark
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Re: Something deeply hidden in the forest

2019-10-15 Thread John Clark

On Tue, Oct 15, 2019 at 1:50 PM 'Brent Meeker' <
everything-list@googlegroups.com> wrote:

>
* > Curiously, Deutsch used a quantum computer in a thought experiment to
> prove multiple worlds.*

He did indeed, I read about it 30 years ago in Deutsch's book "The Ghost In
The Atom" and that was when I started to take the MWI seriously. Deutsch's
test would be very difficult to perform but the reason it's so difficult is
not the Many World's fault, the reason is that the conventional view says
conscious observers obey different laws of physics, Many Worlds says they
do not, so to test who's right we need a mind that uses quantum properties.
Quantum Computers have advanced enormously over the last 30 years so I
wouldn't be surprised if it or something very much like it is actually
performed in a decade or two.

An intelligent quantum computer shoots photons at a metal plate one at a
time that has 2 small slits in it, and then the photons hit a photographic
plate. Nobody looks at the photographic plate till the very end of the
experiment. The quantum mind has detectors near each slit so it knows which
slit the various photons went through. After each photon passes the slits
but before they hit the photographic plate the quantum mind signs a
document saying that it has observed each and every photon and knows which
slit each photon went through. It is very important that the document does
NOT say which slit any photon went through, it only says that they went
through one slit and only one slit and the mind has knowledge of which
one. There is a signed document to this effect for every photon it shoots.

Now the mind uses quantum erasure to completely destroy its memory of which
slit any of the photons went through; the only part remaining in the
universe is the document which states that each photon went through one and
only one slit and the mind (at the time) knew which one. Now develop the
photographic plate and look at it. If you see interference bands then the
Many World interpretation is correct. If you do not see interference bands
then there are no worlds but this one and the conventional quantum
interpretation is correct.

This works because in the Copenhagen interpretation when the results of a
measurement enters the consciousness of an observer the wave function
collapses, in effect all the universes except one disappear without a trace
so you get no interference. In the Many Worlds model all the other worlds
will converge back into one universe because information on which slit the
various photons went through was the only thing that made one universe
different from another, so when that was erased they became identical again
and merged, but their influence will still be felt, you'll see ambiguous
evidence that the photon went through slot A only and ambiguous evidence it
went through slot B only, and that's what causes the interference pattern.

John K Clark

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Re: Something deeply hidden in the forest

2019-10-15 Thread John Clark

On Mon, Oct 14, 2019 at 6:22 PM 'Brent Meeker'  <
everything-list@googlegroups.com> wrote:

>>This is physics not mathematics, the Born rule isn't derived it's
>> observed, and it's observed to work.
>
>
> * > But then MWI can't claim to be simpler and "purer" than CI. *
>

CI says the laws of physics work one way if a system is not observed and
another way if it is observed, and it never makes clear what observed
means. The MWI says the laws of physics only work one way and it makes
crystal clear what observed means. And I don't know about purer but MWI is
certainly simpler than interpretations that are compelled to add extra
terms to Schrodinger's Equation that, other than get rid of other worlds,
do nothing but complicate a already hideously complicated calculation.

> >> I like Many Worlds because it gives me a little intuitive
>> understanding why we can only make probabilistic predictions even though
>> the underlying mathematics is completely deterministic, and I like it
>> because it gives a precise definition of "measurement".
>
>

*> That your consciousness becomes correlated with an eigenvalue of some
> Hermitean operator?*
>

No.

>  > Does MWI define when a measurement has taken place or not?
>

It does.

> > *What is this precise definition of which you write? *
>

Oh for christ sake! As I've said over and over, in Many Worlds a change,
any change, is equivalent to a measurement and it doesn't make the
slightest difference if that change involves consciousness or not. If Brent
Meeker flips a coin and it comes out heads then obviously that Brent Meeker
is not living in the world where it came out tails. In the same way if you
do the two slit experiment and the photon goes through slit A then you are
not living in the world where it went through slot B, but the 2 slit
experiment can be a little different from
the simple coin toss example.

If after the photon makes its decision on which of the 2 slits to go
through it then hits a photographic plate then both photons in both
universes are destroyed and thus there is no longer any difference between
the two, so the universes will merge back together. So in that newly
re-merged universe there will be ambiguity about which slit the photon
actually went through which is why that photon will contribute to  the
interference pattern that shows up on the photographic plate. The important
thing is that the photographic plate destroys the photon in both universes
so you could replace the plate with a brick wall and the same thing would
happen, it would just be harder to tell that something funny was going on.

However if you had a detector next to each slit and sent information on
which slit the photon went through to your computer then there would still
be a physical difference between universes even though the photon no longer
exists in either, one universe would have computer in it with a few
magnetic spots on its disk drive indicating the photon went through slot A
but in the other universe the magnetic spots would be in a slightly
different place indicating slot B, so the universes remain different, so
they don't remerge, so there is no ambiguity in either universe, so neither
universe will see a interference pattern.

Universes don't usually merge back together because the differences between
them usually accelerates so it's astronomically unlikely they will ever
become identical again, however a skilled experimenter can make the change
to be very small and then can gently nudge them back together.  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 universes, and you, will
split and never recombine, and so of course you will see no interference
effect. The beautiful part of the theory is that it doesn't have to explain
what an observer is and that's why a brick wall will work just as well as a
photographic plate.

John K Clark

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Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 12:50:53 PM UTC-5, Brent wrote:
>
>
>
> On 10/15/2019 10:46 AM, Philip Thrift wrote: 
> > 
> > Or: I have yet to see any Many Worlds (Carroll's, Everett's, ...) used 
> > in the actual programming in quantum modeling software. 
> > 
> > Where is it? (Surprise me.) 
>
> Curiously, Deutsch used a quantum computer in a thought experiment to 
> prove multiple worlds. 
>
> Brent 
>



Not the same thing though as a repository of source code (with a Many 
Worlds algorithms library). 


@philipthrift

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Re: Something deeply hidden in the forest

2019-10-15 Thread 'Brent Meeker' via Everything List





On 10/15/2019 10:46 AM, Philip Thrift wrote:


Or: I have yet to see any Many Worlds (Carroll's, Everett's, ...) used 
in the actual programming in quantum modeling software.


Where is it? (Surprise me.)


Curiously, Deutsch used a quantum computer in a thought experiment to 
prove multiple worlds.


Brent

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Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 12:26:55 PM UTC-5, Philip Thrift wrote:
>
>
>
> On Tuesday, October 15, 2019 at 10:26:15 AM UTC-5, Lawrence Crowell wrote:
>>
>> On Tuesday, October 15, 2019 at 6:02:15 AM UTC-5, Philip Thrift wrote:
>>>
>>>
>>>
>>> On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:

 On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell 
> wrote:
>>
>> On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>>>
>>> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
>>> wrote:
>>>
 On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:
>
> Part of the dislike of the MWI is that its proponents assume a 
> purity that is not an evident virtue of the intepretation.  For 
> example, 
> interpreting the squared amplitudes as probabilities seems to be 
> assumed, 
> along with the existence of the preferred basis in which the 
> amplitudes are 
> defined.  Together these are almost the same as CI.  If you ask 
> "probabilities of what?" in MWI the answer can't be probability of 
> existing 
> because MWI has committed to all solutions, however improbable, 
> existing.  
> So it becomes probability of finding yourself in a particular 
> world...which 
> depends on a theory of consciousness and seems to regress to von 
> Neumann 
> and Wigner.
>
> Zurek's envariance attempts to answer these questions and provide 
> a justification for preferred bases and what probability refers to.  
> But 
> notice that to the extent he succeeds he is justifying taking a 
> simple 
> probabilistic view and saying one of those preferred states happens 
> and the 
> others don't.
>
> Brent
>
>
>
 In the single-particle double-slit experiment*, an observer could 
 see a dot appear anywhere on a screen where path interference does not 
 reduce the probability to zero. So with the literal 
 many-world-branching 
 theory, how many different worlds are produced, each on with its own 
 observer seeing a dot on the screen?

>>>
>>> According to MWI, an infinite number. Each world will have the dot 
>>> at a different place on the screen.
>>>
>>> Bruce
>>>
>>
>> What you say may open up a bit of a hole or snag in MWI. This is 
>> something I have been pondering some since Carroll's popularization. If 
>> MWI 
>> fundamentally preserves unitarity by splitting off worlds then 
>> localization 
>> of a measurement is an illusion.Consider a particle measured somewhere 
>> on a 
>> path from x and x'.  The path integral and the nonlocality of paths is a 
>> sum over all possible measurements in all space containing x and x', 
>> then 
>> there must be a continuum of possible worlds splitting off. If the 
>> operator 
>> has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
>> continuum of possible worlds if there is indeed no fundamental 
>> localization 
>> with a measurement. This is not just infinite, but uncountably infinite.
>>
>> This is different from how decoherence maintains unitarity and 
>> conserves qubits. There a local interaction occurs that induces quantum 
>> phase to enter into a set of ancillary states or reservoir of states. 
>> Then 
>> we can consider quantum states as finite, but unbounded from above, so 
>> that 
>> local observations and measurements are possible. 
>>
>> This does seem to run into some oddities that either need to be 
>> worked out or that might indicate some gap in MWI. The persistence of 
>> nonlocality in MWI is interesting for possible quantum gravitation work. 
>> In 
>> that case I can think of maybe a way around this, where this uncountably 
>> infinite set of g_{ij} configurations, or Ψ[g_{ij}], can be identified 
>> with 
>> "exotic" manifolds that are removed. It is less clear how this can 
>> happen 
>> with ordinary quantum fields that have local realizations.
>>
>> LC
>>
>
>
>
> To mix an analysis (or a theory) of the path integral with an analysis 
> (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
> that only leads to confusion.
>
> @philipthrift 
>

 I am thinking of a path integral as most physicists do, which is an 
 action principle that is a sum over amplitudes or histories. You are 
 thinking according to the quantum interpretation of Dowker and others, 
 which has auxiliary postulates or assumptions.

Re: Yes, it's true. Theoretical physics has become a lunatic asylum.



On Tuesday, October 15, 2019 at 7:46:07 AM UTC-5, Bruno Marchal wrote:
>
>
>  But never mind, especially that with Mechanism, there are no world at 
> all, just “numbers”, together with + and *.
>
>
> Bruno
>
>
>
That's certainly better than MWI.

@philipthrift 

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Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 11:06:07 AM UTC-5, Brent wrote:
>
>
>
> On 10/15/2019 4:08 AM, Philip Thrift wrote: 
> > 
> > Also see Feynman's Meaning of Probabilities in QM paper. 
> > 
> > But there are no probabilities in MWI. 
>
> There are, but you have to put them in there essentially by slipping the 
> Born rule in the back door. 
>
> Brent 
>
> > 
> > You can't take a probabilistic theory and gloss it onto MWI. 
> > 
> > (like putting lipstick on a pig) 
>


There is no "no nonsense" way to assign probabilities to worlds in MWI.

May to the bubble worlds of cosmic inflation, but that's a totally 
different domain.

@philipthrift 

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Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 10:28:09 AM UTC-5, Lawrence Crowell wrote:
>
> On Tuesday, October 15, 2019 at 6:08:27 AM UTC-5, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, October 15, 2019 at 6:02:15 AM UTC-5, Philip Thrift wrote:
>>>
>>>
>>>
>>> On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:

 On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell 
> wrote:
>>
>> On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>>>
>>> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
>>> wrote:
>>>
 On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:
>
> Part of the dislike of the MWI is that its proponents assume a 
> purity that is not an evident virtue of the intepretation.  For 
> example, 
> interpreting the squared amplitudes as probabilities seems to be 
> assumed, 
> along with the existence of the preferred basis in which the 
> amplitudes are 
> defined.  Together these are almost the same as CI.  If you ask 
> "probabilities of what?" in MWI the answer can't be probability of 
> existing 
> because MWI has committed to all solutions, however improbable, 
> existing.  
> So it becomes probability of finding yourself in a particular 
> world...which 
> depends on a theory of consciousness and seems to regress to von 
> Neumann 
> and Wigner.
>
> Zurek's envariance attempts to answer these questions and provide 
> a justification for preferred bases and what probability refers to.  
> But 
> notice that to the extent he succeeds he is justifying taking a 
> simple 
> probabilistic view and saying one of those preferred states happens 
> and the 
> others don't.
>
> Brent
>
>
>
 In the single-particle double-slit experiment*, an observer could 
 see a dot appear anywhere on a screen where path interference does not 
 reduce the probability to zero. So with the literal 
 many-world-branching 
 theory, how many different worlds are produced, each on with its own 
 observer seeing a dot on the screen?

>>>
>>> According to MWI, an infinite number. Each world will have the dot 
>>> at a different place on the screen.
>>>
>>> Bruce
>>>
>>
>> What you say may open up a bit of a hole or snag in MWI. This is 
>> something I have been pondering some since Carroll's popularization. If 
>> MWI 
>> fundamentally preserves unitarity by splitting off worlds then 
>> localization 
>> of a measurement is an illusion.Consider a particle measured somewhere 
>> on a 
>> path from x and x'.  The path integral and the nonlocality of paths is a 
>> sum over all possible measurements in all space containing x and x', 
>> then 
>> there must be a continuum of possible worlds splitting off. If the 
>> operator 
>> has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
>> continuum of possible worlds if there is indeed no fundamental 
>> localization 
>> with a measurement. This is not just infinite, but uncountably infinite.
>>
>> This is different from how decoherence maintains unitarity and 
>> conserves qubits. There a local interaction occurs that induces quantum 
>> phase to enter into a set of ancillary states or reservoir of states. 
>> Then 
>> we can consider quantum states as finite, but unbounded from above, so 
>> that 
>> local observations and measurements are possible. 
>>
>> This does seem to run into some oddities that either need to be 
>> worked out or that might indicate some gap in MWI. The persistence of 
>> nonlocality in MWI is interesting for possible quantum gravitation work. 
>> In 
>> that case I can think of maybe a way around this, where this uncountably 
>> infinite set of g_{ij} configurations, or Ψ[g_{ij}], can be identified 
>> with 
>> "exotic" manifolds that are removed. It is less clear how this can 
>> happen 
>> with ordinary quantum fields that have local realizations.
>>
>> LC
>>
>
>
>
> To mix an analysis (or a theory) of the path integral with an analysis 
> (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
> that only leads to confusion.
>
> @philipthrift 
>

 I am thinking of a path integral as most physicists do, which is an 
 action principle that is a sum over amplitudes or histories. You are 
 thinking according to the quantum interpretation of Dowker and others, 
 which has auxiliary postulates or assumptions.

Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 10:26:15 AM UTC-5, Lawrence Crowell wrote:
>
> On Tuesday, October 15, 2019 at 6:02:15 AM UTC-5, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:
>>>
>>> On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:



 On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell wrote:
>
> On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>>
>> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
>> wrote:
>>
>>> On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:

 Part of the dislike of the MWI is that its proponents assume a 
 purity that is not an evident virtue of the intepretation.  For 
 example, 
 interpreting the squared amplitudes as probabilities seems to be 
 assumed, 
 along with the existence of the preferred basis in which the 
 amplitudes are 
 defined.  Together these are almost the same as CI.  If you ask 
 "probabilities of what?" in MWI the answer can't be probability of 
 existing 
 because MWI has committed to all solutions, however improbable, 
 existing.  
 So it becomes probability of finding yourself in a particular 
 world...which 
 depends on a theory of consciousness and seems to regress to von 
 Neumann 
 and Wigner.

 Zurek's envariance attempts to answer these questions and provide a 
 justification for preferred bases and what probability refers to.  But 
 notice that to the extent he succeeds he is justifying taking a simple 
 probabilistic view and saying one of those preferred states happens 
 and the 
 others don't.

 Brent



>>> In the single-particle double-slit experiment*, an observer could 
>>> see a dot appear anywhere on a screen where path interference does not 
>>> reduce the probability to zero. So with the literal 
>>> many-world-branching 
>>> theory, how many different worlds are produced, each on with its own 
>>> observer seeing a dot on the screen?
>>>
>>
>> According to MWI, an infinite number. Each world will have the dot at 
>> a different place on the screen.
>>
>> Bruce
>>
>
> What you say may open up a bit of a hole or snag in MWI. This is 
> something I have been pondering some since Carroll's popularization. If 
> MWI 
> fundamentally preserves unitarity by splitting off worlds then 
> localization 
> of a measurement is an illusion.Consider a particle measured somewhere on 
> a 
> path from x and x'.  The path integral and the nonlocality of paths is a 
> sum over all possible measurements in all space containing x and x', then 
> there must be a continuum of possible worlds splitting off. If the 
> operator 
> has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
> continuum of possible worlds if there is indeed no fundamental 
> localization 
> with a measurement. This is not just infinite, but uncountably infinite.
>
> This is different from how decoherence maintains unitarity and 
> conserves qubits. There a local interaction occurs that induces quantum 
> phase to enter into a set of ancillary states or reservoir of states. 
> Then 
> we can consider quantum states as finite, but unbounded from above, so 
> that 
> local observations and measurements are possible. 
>
> This does seem to run into some oddities that either need to be worked 
> out or that might indicate some gap in MWI. The persistence of 
> nonlocality 
> in MWI is interesting for possible quantum gravitation work. In that case 
> I 
> can think of maybe a way around this, where this uncountably infinite set 
> of g_{ij} configurations, or Ψ[g_{ij}], can be identified with "exotic" 
> manifolds that are removed. It is less clear how this can happen with 
> ordinary quantum fields that have local realizations.
>
> LC
>



 To mix an analysis (or a theory) of the path integral with an analysis 
 (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
 that only leads to confusion.

 @philipthrift 

>>>
>>> I am thinking of a path integral as most physicists do, which is an 
>>> action principle that is a sum over amplitudes or histories. You are 
>>> thinking according to the quantum interpretation of Dowker and others, 
>>> which has auxiliary postulates or assumptions.
>>>
>>> LC 
>>>
>>
>> Path integrals or histories are  not eve brought up in Sean Carroll's 
>> book (a search of the text shows).
>>
>> So they not present in any way in MWI.
>>
>> MWI (in Sean's mathematical formulation) is contrary to the

Re: Yes, it's true. Theoretical physics has become a lunatic asylum.

2019-10-15 Thread 'Brent Meeker' via Everything List





On 10/15/2019 5:43 AM, Bruno Marchal wrote:


Imagine the WM-duplication, or better here, a guy who is duplicated 
in two virtual rooms, numerically identical, except for a close 
virtual envelop with a paper containing 1 (written on a paper)  in 
room 1 and 2 in room 2.


If the person there does not open the envelop, we can fuse them 
again, and nothing special happened. It one consciousness flux, like 
if no duplication occurred.
But if the guy open the envelop and read what is on the paper, then 
the consciousness flux differentiates.


Which is the QBist interpretation of QM.


Cool!

If you have a best link on QBism, I might be interested (but I might 
ask again later, as I have not much time to do research right now).


https://arxiv.org/pdf/1412.4211.pdf

https://arxiv.org/pdf/0706.2661.pdf

Brent

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Re: Something deeply hidden in the forest

2019-10-15 Thread 'Brent Meeker' via Everything List





On 10/15/2019 4:08 AM, Philip Thrift wrote:


Also see Feynman's Meaning of Probabilities in QM paper.

But there are no probabilities in MWI.


There are, but you have to put them in there essentially by slipping the 
Born rule in the back door.


Brent



You can't take a probabilistic theory and gloss it onto MWI.

(like putting lipstick on a pig)


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Re: Something deeply hidden in the forest

On Tuesday, October 15, 2019 at 6:08:27 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Tuesday, October 15, 2019 at 6:02:15 AM UTC-5, Philip Thrift wrote:
>>
>>
>>
>> On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:
>>>
>>> On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:



 On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell wrote:
>
> On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>>
>> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
>> wrote:
>>
>>> On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:

 Part of the dislike of the MWI is that its proponents assume a 
 purity that is not an evident virtue of the intepretation.  For 
 example, 
 interpreting the squared amplitudes as probabilities seems to be 
 assumed, 
 along with the existence of the preferred basis in which the 
 amplitudes are 
 defined.  Together these are almost the same as CI.  If you ask 
 "probabilities of what?" in MWI the answer can't be probability of 
 existing 
 because MWI has committed to all solutions, however improbable, 
 existing.  
 So it becomes probability of finding yourself in a particular 
 world...which 
 depends on a theory of consciousness and seems to regress to von 
 Neumann 
 and Wigner.

 Zurek's envariance attempts to answer these questions and provide a 
 justification for preferred bases and what probability refers to.  But 
 notice that to the extent he succeeds he is justifying taking a simple 
 probabilistic view and saying one of those preferred states happens 
 and the 
 others don't.

 Brent



>>> In the single-particle double-slit experiment*, an observer could 
>>> see a dot appear anywhere on a screen where path interference does not 
>>> reduce the probability to zero. So with the literal 
>>> many-world-branching 
>>> theory, how many different worlds are produced, each on with its own 
>>> observer seeing a dot on the screen?
>>>
>>
>> According to MWI, an infinite number. Each world will have the dot at 
>> a different place on the screen.
>>
>> Bruce
>>
>
> What you say may open up a bit of a hole or snag in MWI. This is 
> something I have been pondering some since Carroll's popularization. If 
> MWI 
> fundamentally preserves unitarity by splitting off worlds then 
> localization 
> of a measurement is an illusion.Consider a particle measured somewhere on 
> a 
> path from x and x'.  The path integral and the nonlocality of paths is a 
> sum over all possible measurements in all space containing x and x', then 
> there must be a continuum of possible worlds splitting off. If the 
> operator 
> has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
> continuum of possible worlds if there is indeed no fundamental 
> localization 
> with a measurement. This is not just infinite, but uncountably infinite.
>
> This is different from how decoherence maintains unitarity and 
> conserves qubits. There a local interaction occurs that induces quantum 
> phase to enter into a set of ancillary states or reservoir of states. 
> Then 
> we can consider quantum states as finite, but unbounded from above, so 
> that 
> local observations and measurements are possible. 
>
> This does seem to run into some oddities that either need to be worked 
> out or that might indicate some gap in MWI. The persistence of 
> nonlocality 
> in MWI is interesting for possible quantum gravitation work. In that case 
> I 
> can think of maybe a way around this, where this uncountably infinite set 
> of g_{ij} configurations, or Ψ[g_{ij}], can be identified with "exotic" 
> manifolds that are removed. It is less clear how this can happen with 
> ordinary quantum fields that have local realizations.
>
> LC
>



 To mix an analysis (or a theory) of the path integral with an analysis 
 (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
 that only leads to confusion.

 @philipthrift 

>>>
>>> I am thinking of a path integral as most physicists do, which is an 
>>> action principle that is a sum over amplitudes or histories. You are 
>>> thinking according to the quantum interpretation of Dowker and others, 
>>> which has auxiliary postulates or assumptions.
>>>
>>> LC 
>>>
>>
>> Path integrals or histories are  not eve brought up in Sean Carroll's 
>> book (a search of the text shows).
>>
>> So they not present in any way in MWI.
>>
>> MWI (in Sean's mathematical formulation) is contrary to the path

Re: Something deeply hidden in the forest

On Tuesday, October 15, 2019 at 6:02:15 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:
>>
>> On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:
>>>
>>>
>>>
>>> On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell wrote:

 On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>
> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
> wrote:
>
>> On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:
>>>
>>> Part of the dislike of the MWI is that its proponents assume a 
>>> purity that is not an evident virtue of the intepretation.  For 
>>> example, 
>>> interpreting the squared amplitudes as probabilities seems to be 
>>> assumed, 
>>> along with the existence of the preferred basis in which the amplitudes 
>>> are 
>>> defined.  Together these are almost the same as CI.  If you ask 
>>> "probabilities of what?" in MWI the answer can't be probability of 
>>> existing 
>>> because MWI has committed to all solutions, however improbable, 
>>> existing.  
>>> So it becomes probability of finding yourself in a particular 
>>> world...which 
>>> depends on a theory of consciousness and seems to regress to von 
>>> Neumann 
>>> and Wigner.
>>>
>>> Zurek's envariance attempts to answer these questions and provide a 
>>> justification for preferred bases and what probability refers to.  But 
>>> notice that to the extent he succeeds he is justifying taking a simple 
>>> probabilistic view and saying one of those preferred states happens and 
>>> the 
>>> others don't.
>>>
>>> Brent
>>>
>>>
>>>
>> In the single-particle double-slit experiment*, an observer could see 
>> a dot appear anywhere on a screen where path interference does not 
>> reduce 
>> the probability to zero. So with the literal many-world-branching 
>> theory, 
>> how many different worlds are produced, each on with its own observer 
>> seeing a dot on the screen?
>>
>
> According to MWI, an infinite number. Each world will have the dot at 
> a different place on the screen.
>
> Bruce
>

 What you say may open up a bit of a hole or snag in MWI. This is 
 something I have been pondering some since Carroll's popularization. If 
 MWI 
 fundamentally preserves unitarity by splitting off worlds then 
 localization 
 of a measurement is an illusion.Consider a particle measured somewhere on 
 a 
 path from x and x'.  The path integral and the nonlocality of paths is a 
 sum over all possible measurements in all space containing x and x', then 
 there must be a continuum of possible worlds splitting off. If the 
 operator 
 has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
 continuum of possible worlds if there is indeed no fundamental 
 localization 
 with a measurement. This is not just infinite, but uncountably infinite.

 This is different from how decoherence maintains unitarity and 
 conserves qubits. There a local interaction occurs that induces quantum 
 phase to enter into a set of ancillary states or reservoir of states. Then 
 we can consider quantum states as finite, but unbounded from above, so 
 that 
 local observations and measurements are possible. 

 This does seem to run into some oddities that either need to be worked 
 out or that might indicate some gap in MWI. The persistence of nonlocality 
 in MWI is interesting for possible quantum gravitation work. In that case 
 I 
 can think of maybe a way around this, where this uncountably infinite set 
 of g_{ij} configurations, or Ψ[g_{ij}], can be identified with "exotic" 
 manifolds that are removed. It is less clear how this can happen with 
 ordinary quantum fields that have local realizations.

 LC

>>>
>>>
>>>
>>> To mix an analysis (or a theory) of the path integral with an analysis 
>>> (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
>>> that only leads to confusion.
>>>
>>> @philipthrift 
>>>
>>
>> I am thinking of a path integral as most physicists do, which is an 
>> action principle that is a sum over amplitudes or histories. You are 
>> thinking according to the quantum interpretation of Dowker and others, 
>> which has auxiliary postulates or assumptions.
>>
>> LC 
>>
>
> Path integrals or histories are  not eve brought up in Sean Carroll's book 
> (a search of the text shows).
>
> So they not present in any way in MWI.
>
> MWI (in Sean's mathematical formulation) is contrary to the path integral, 
> because histories (as you mention above) are simply not worlds (in Sean's 
> formulation).
>
> @philipthrift 
>

Path integrals are just methods. Three is nothing any different from QM or

Re: The multiverse almost everyone believes in


> On 14 Oct 2019, at 03:20, spudboy100 via Everything List 
>  wrote:
> 
> Sort of like the Boltzmann Brain thing where Bruno suspect is irrelevant. I 
> don't mind irrelevancy, but do like the idea of the BB being,  Mr. God Sir!
> https://www.thoughtco.com/what-are-boltzmann-brains-2699421 
> 

The BB requires many hypothesis, but they can illustrate the mind-body problem 
for physicalist.

Arithmetic emulates already all possible brains, Botzmann or not.

That can be proved in one line … from Gödel’s 1931 paper.

Bruno



> 
> 
> -Original Message-
> From: smitra 
> To: everything-list 
> Sent: Sun, Oct 13, 2019 11:26 am
> Subject: The multiverse almost everyone believes in
> 
> Most people believe in either block time or presentism.  Few people 
> believe that the past never really existed. One can, e.g. believe that 
> God created the universe ten minutes ago which would mean that all our 
> memories of events that took place earlier are false memories. The 
> universe came into being ten minutes ago including us with all our false 
> memories of the events that actually never happened. If we then assume 
> that the past and the future are/were/will be real (whatever that 
> means), then that defines a multiverse of Worlds labeled by the time 
> variable.
> 
> 
> Saibal
> 
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Re: Yes, it's true. Theoretical physics has become a lunatic asylum.


> On 14 Oct 2019, at 21:46, 'Brent Meeker' via Everything List 
>  wrote:
> 
> 
> 
> On 10/14/2019 11:42 AM, Philip Thrift wrote:
>> 
>> 
>> On Monday, October 14, 2019 at 1:28:26 PM UTC-5, Brent wrote:
>> 
>> Which is the QBist interpretation of QM.   [ Re: Gödel-Löb-Solovay 
>> “theology”]
>> 
>> Brent
>> 
>> 
>> 
>> MWI is QB on steroids.
> 
> I'd say it's MWI plus humility.

I’d say the contrary. Usually, to accept more people and histories seems to me 
more humble than the belief in own own uniqueness …. But never mind, especially 
that with Mechanism, there are no world at all, just “numbers”, together with + 
and *.

Bruno



> 
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Re: Yes, it's true. Theoretical physics has become a lunatic asylum.


> On 14 Oct 2019, at 20:28, 'Brent Meeker' via Everything List 
>  wrote:
> 
> 
> 
> On 10/14/2019 7:20 AM, Bruno Marchal wrote:
>> 
>>> On 11 Oct 2019, at 01:23, 'Brent Meeker' via Everything List 
>>> >> > wrote:
>>> 
>>> 
>>> 
>>> On 10/6/2019 3:03 AM, smitra wrote:
> 
> And with finite information in the universe there is not distinction 
> between recurrences and hence there are no recurrences. 
> 
 
 Yes, but there will also be imperfect recurrences where the difference 
 will go unnoticed for an observer until a measurement is made. You can 
 then have an effective splitting in single world collapse theories. and 
 each outcome will have a certain probability that corresponds to the 
 relative frequency at which different outcomes will occur in a large time 
 period.
>>> 
>>> What does "effective splitting in single world collapse" mean?  Sounds like 
>>> classical probability due to ignorance...except that's NOT splitting.
>> 
>> 
>> It is differentiating.
>> 
>> Imagine the WM-duplication, or better here, a guy who is duplicated in two 
>> virtual rooms, numerically identical, except for a close virtual envelop 
>> with a paper containing 1 (written on a paper)  in room 1 and 2 in room 2.
>> 
>> If the person there does not open the envelop, we can fuse them again, and 
>> nothing special happened. It one consciousness flux, like if no duplication 
>> occurred. 
>> But if the guy open the envelop and read what is on the paper, then the 
>> consciousness flux differentiates.
> 
> Which is the QBist interpretation of QM.

Cool!

If you have a best link on QBism, I might be interested (but I might ask again 
later, as I have not much time to do research right now).

Bruno


> 
> Brent
> 
>> 
>> For the measure on the histories, the rule is graphically sum up by the 
>> diagram:
>> 
>>   Y   =II
>> 
>> The differentiation in the future separate the past, and it allows the 
>> elimination of the splitting. The real diagram are provided by the Kripke 
>> semantic, or other semantic for the modal logic of self-reference (and its 
>> intensional variants), where we should get something like the Feynman 
>> diagrams for the histories and sub-histories.
>> 
>> Like you say: it is classical probabilities, from a relative first person 
>> perspective, localised in a mathematically sophisticated structure. The 
>> many-worlds of the universal wave seems to confirm the many-computations of 
>> elementary arithmetic. This one has the Gödel-Löb-Solovay “theology” capable 
>> of distinguishing quanta (knowable, observable and sharable) from qualia 
>> (knowable, observable, but not sharable).
>> 
>> Bruno
>> 
>> 
>> 
>> 
>> 
>>> 
>>> Brent
>>> 
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>> 
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> 
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Re: Yes, it's true. Theoretical physics has become a lunatic asylum.


> On 14 Oct 2019, at 20:06, Philip Thrift  wrote:
> 
> 
> 
> On Monday, October 14, 2019 at 9:20:28 AM UTC-5, Bruno Marchal wrote:
> 
>> On 11 Oct 2019, at 01:23, 'Brent Meeker' via Everything List 
>> > wrote:
>> 
>> 
>> 
>> On 10/6/2019 3:03 AM, smitra wrote:
 
 And with finite information in the universe there is not distinction 
 between recurrences and hence there are no recurrences. 
 
>>> 
>>> Yes, but there will also be imperfect recurrences where the difference will 
>>> go unnoticed for an observer until a measurement is made. You can then have 
>>> an effective splitting in single world collapse theories. and each outcome 
>>> will have a certain probability that corresponds to the relative frequency 
>>> at which different outcomes will occur in a large time period.
>> 
>> What does "effective splitting in single world collapse" mean?  Sounds like 
>> classical probability due to ignorance...except that's NOT splitting.
> 
> 
> It is differentiating.
> 
> Imagine the WM-duplication, or better here, a guy who is duplicated in two 
> virtual rooms, numerically identical, except for a close virtual envelop with 
> a paper containing 1 (written on a paper)  in room 1 and 2 in room 2.
> 
> If the person there does not open the envelop, we can fuse them again, and 
> nothing special happened. It one consciousness flux, like if no duplication 
> occurred. 
> But if the guy open the envelop and read what is on the paper, then the 
> consciousness flux differentiates.
> 
> For the measure on the histories, the rule is graphically sum up by the 
> diagram:
> 
>   Y   =II
> 
> The differentiation in the future separate the past, and it allows the 
> elimination of the splitting. The real diagram are provided by the Kripke 
> semantic, or other semantic for the modal logic of self-reference (and its 
> intensional variants), where we should get something like the Feynman 
> diagrams for the histories and sub-histories.
> 
> Like you say: it is classical probabilities, from a relative first person 
> perspective, localised in a mathematically sophisticated structure. The 
> many-worlds of the universal wave seems to confirm the many-computations of 
> elementary arithmetic. This one has the Gödel-Löb-Solovay “theology” capable 
> of distinguishing quanta (knowable, observable and sharable) from qualia 
> (knowable, observable, but not sharable).
> 
> Bruno
> 
> 
> 
> Many Words is Gödel-Löb-Solovay “theology.
> 
> Of course!

If this is not sarcastic: no. That is not obvious. But it is explained in all 
details in my papers, but you might need to study some good book in logic (like 
Mendelson’s one already referred to).

Bruno



> 
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Re: Superposition Misinterpreted

> On 14 Oct 2019, at 17:11, Alan Grayson  wrote:
> 
> 
> 
> On Monday, October 14, 2019 at 3:40:01 AM UTC-6, Philip Thrift wrote:
> 
> 
> On Sunday, October 13, 2019 at 11:10:58 PM UTC-5, Alan Grayson wrote:
> 
> 
> On Sunday, October 13, 2019 at 5:50:35 PM UTC-6, Brent wrote:
> 
> 
> On 10/13/2019 1:08 PM, Alan Grayson wrote: 
> > What are YOU talking about? I just made a GUESS about the decoherence 
> > time! Whatever it is, it doesn't change my conclusion. If there's a 
> > uncertainty in time, are you claiming the cat can be alive and dead 
> > during any duration?  Is this what decoherence theory offers? AG 
> 
> Yes, part of the cat can be alive and part dead over a period seconds.  
> Or looked at another way, there is a transistion period in which the cat 
> is both alive and dead. 
> 
> But the main point is that this time had nothing to do with 
> Schroedinger's argument (he knew perfectly well the time of death was 
> vague); his argument was that Bohr's interpretation implied that the cat 
> was in a super-position of alive and dead from the time the box was 
> closed until someone looked in. 
> 
> Brent 
> 
> Agreed. Without decoherence, the cat would be in a superposition of
> alive and dead from the time the box was closed until someone opened
> it. With decoherence, it would be in that superposition for a very short
> time, the decoherence time, when it would be in state, |decayed>|dead>
> or |undecayed> |alive> before the box was opened, provided it was
> opened after the decoherence time. So, as I see it, decoherence just
> moves the "collapse" earlier, before the box is opened, and does not
> resolve S's problem with superposition. The cause of the problem, or
> paradox if you will, is the superposition interpretation of the radioactive
> source. AG  
> 
> 
> 
> How would you describe the "states" of qubits in IBM's Q (quantum computer)? 
> 
> @philipthrift
> 
> I am not familiar with the theory on which quantum computers are based, so I 
> cannot answer this question. AG 

A quantum computer is just that, a computer that you can put in superposition 
state. You can put any bit in any arbitrary superposition state, like being 0 
and 1 “simultaneously”. You can put the whole processor in a superposition 
state, even in the on/off superposition state. With a 64 quit computer, you can 
do 2^64 computations simultaneously, and then you can make a Fourier transform 
of all results, and get some information. Shor’s algorithm, to factorise large 
number, use such large superposition. 
David Deutsch invented it mainly to illustrate that we have to take the 
superposition state seriously, but of course e know this since at least Dirac.

The technical difficulty is to get those stable, but progress have shown that 
it is possible, notably through quantum correction code (software solution) or 
through topological quantum computing (by squeezing electron in some way, we 
can build very stable superposition, unfortunately, the “squeezing apparatus” 
have to be huge, and this is not for tomorrow. But like Shannon theorem showed 
that we can transmit information  on wires, the quantum correcting code 
technics refutes many impossibility statements once made in that field.  That 
is why so many work on this.

Bruno

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Re: Superposition Misinterpreted


> On 13 Oct 2019, at 21:19, 'Brent Meeker' via Everything List 
>  wrote:
> 
> 
> 
> On 10/13/2019 6:48 AM, Bruno Marchal wrote:
>> 
>>> On 9 Oct 2019, at 12:52, Alan Grayson >> > wrote:
>>> 
>>> 
>>> 
>>> On Wednesday, October 9, 2019 at 12:28:38 AM UTC-6, Brent wrote:
>>> 
>>> 
>>> On 10/8/2019 9:20 PM, Alan Grayson wrote: 
>>> > I've argued this before, but it's worth stating again. It's a 
>>> > misintepretation of superposition to claim that a system described by 
>>> > it, is in all the component states simultaneously. As is easily seen 
>>> > in ordinary vector space, an arbitrary vector has an uncountable 
>>> > number of different representations. Thus, to claim it is in some 
>>> > specific set of component states simultaneously, makes no sense. Thus 
>>> > evaporates a key "mystery" of quantum theory, inclusive of S's cat and 
>>> > Everett's many worlds. AG 
>>> 
>>> No.  It changes the problem to the question of why there are preferred 
>>> bases. 
>>> 
>>> Brent 
>>> 
>>> Who chose Alive and Dead, or Awake and Sleeping for the S. cat? Wasn't it 
>>> the observer? Since they had other choices, my claim stands. AG 
>> 
>> Everett showed explicitly that the relative states, and their relative 
>> statistics does not depend on the choice of the bases.
>> Something quite similar occur already in arithmetic, with a much general 
>> notion of "base”.
> 
> But he didn't explain why observations were only possible in some bases.

Which is something that I doubt about. Maybe this is just false. Only Zurel 
makes me think that the position base is more important … for us (the human), 
but other bases might play a similar role. For me this is an open problem.

Bruno



> 
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Re: Superposition Misinterpreted



> On 13 Oct 2019, at 21:17, 'Brent Meeker' via Everything List 
>  wrote:
> 
> 
> 
> On 10/13/2019 6:44 AM, Bruno Marchal wrote:
>>> On 9 Oct 2019, at 08:28, 'Brent Meeker' via Everything List 
>>>  wrote:
>>> 
>>> 
>>> 
>>> On 10/8/2019 9:20 PM, Alan Grayson wrote:
 I've argued this before, but it's worth stating again. It's a 
 misintepretation of superposition to claim that a system described by it, 
 is in all the component states simultaneously. As is easily seen in 
 ordinary vector space, an arbitrary vector has an uncountable number of 
 different representations. Thus, to claim it is in some specific set of 
 component states simultaneously, makes no sense. Thus evaporates a key 
 "mystery" of quantum theory, inclusive of S's cat and Everett's many 
 worlds. AG
>>> No.  It changes the problem to the question of why there are preferred 
>>> bases.
>> There are no preferred base. Or, if you prefer, such base are chosen by the 
>> entities which can be conscious, or compute, relatively to such base.
> 
> For someone who claims to have shown that physics is derivative from 
> psychology that should count as fundamentally preferred.

Psychology is not a base. Then, if we assume that the brain is Turing emulable, 
it is necessary that physics has to be explained from psychology, or better 
theology. That is the first result, and the second result is that we get 
quantum logic at the places expected. We get three different quantum logic, all 
richer than the usual inferred from nature, so we will learn more with the 
possible futures experiences.

Bruno




> 
> Brent
> 
>> Then there are some explanation why such bases favour the position 
>> observable, like the analysis by Zurek of decoherence.
>> 
>> Bruno
>> 
>> 
>> 
>>> Brent
>>> 
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Re: Superposition Misinterpreted


> On 13 Oct 2019, at 16:43, Alan Grayson  wrote:
> 
> 
> 
> On Sunday, October 13, 2019 at 7:48:29 AM UTC-6, Bruno Marchal wrote:
> 
>> On 9 Oct 2019, at 12:52, Alan Grayson > 
>> wrote:
>> 
>> 
>> 
>> On Wednesday, October 9, 2019 at 12:28:38 AM UTC-6, Brent wrote:
>> 
>> 
>> On 10/8/2019 9:20 PM, Alan Grayson wrote: 
>> > I've argued this before, but it's worth stating again. It's a 
>> > misintepretation of superposition to claim that a system described by 
>> > it, is in all the component states simultaneously. As is easily seen 
>> > in ordinary vector space, an arbitrary vector has an uncountable 
>> > number of different representations. Thus, to claim it is in some 
>> > specific set of component states simultaneously, makes no sense. Thus 
>> > evaporates a key "mystery" of quantum theory, inclusive of S's cat and 
>> > Everett's many worlds. AG 
>> 
>> No.  It changes the problem to the question of why there are preferred 
>> bases. 
>> 
>> Brent 
>> 
>> Who chose Alive and Dead, or Awake and Sleeping for the S. cat? Wasn't it 
>> the observer? Since they had other choices, my claim stands. AG 
> 
> Everett showed explicitly that the relative states, and their relative 
> statistics does not depend on the choice of the bases.
> Something quite similar occur already in arithmetic, with a much general 
> notion of "base”.
> 
> Bruno
> 
> Arithmetic does not include probability theory. AG 

In the arithmetical ontology? You are right.

But if we assume mechanism, it is not difficult to explain why many form of 
uncertainty measure appears in the phenomenology of mind and matter from the 
person associated to number in the computations (realised in arithmetic). This 
is usually what I explain in the first half on my papers on this subject. Ask 
me any question starting from the papers. I have not much time until the end of 
November to explain it here.

Bruno



> 
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Re: Superposition Misinterpreted


> On 13 Oct 2019, at 16:36, Alan Grayson  wrote:
> 
> 
> 
> On Sunday, October 13, 2019 at 12:00:53 AM UTC-6, Alan Grayson wrote:
> 
> 
> On Saturday, October 12, 2019 at 11:48:33 PM UTC-6, Alan Grayson wrote:
> 
> 
> On Saturday, October 12, 2019 at 11:30:19 PM UTC-6, Brent wrote:
> 
> 
> On 10/12/2019 7:21 PM, Alan Grayson wrote:
>> 
>> 
>> On Saturday, October 12, 2019 at 8:07:46 PM UTC-6, Brent wrote:
>> 
>> 
>> On 10/12/2019 5:46 PM, Alan Grayson wrote:
 
 What does "realized" mean?  made real?  Being real is a metaphysical 
 concept.  Bohr never said anything about components of a superposition 
 being real.  He famously said “Physics is not about how the world is, it 
 is about what we can say about the world” and “Everything we call real is 
 made of things that cannot be regarded as real.”
 
 Brent
 
 The latter comment is ridiculous. Aren't protons, neutrons and electrons 
 real?
>>> 
>>> Ask Bohr.  You never answer my questions; why should I answer yours.
>>> 
>>> Brent
>>> 
>>> What questions haven't I answered??? AG 
>> 
>> Scan up until you see this symbol "?"
>> 
>> Brent
>> 
>> I explained what "realized" means by giving an example; S's cat, alive and 
>> dead simultaneously.
> 
> That's a representation in the theory.  Every measurement that "realizes" its 
> state finds it to be one or the other.  So what's the operational 
> significance of "being realized"?  Schroedinger's whole point was that an 
> alive and dead cat is never realized.
> 
> Brent
> 
> As I previously suggested, since there is no operator that has those cat 
> states as eigenstates, S's example was probably meant to falsify the then 
> prevailing (and continuing) interpretation of superposition, as it leads to 
> an absurdity. It's not just about the cat! But the case of spin could be an 
> exception to my general claim that it's a fallacy to interpret a 
> superposition to mean the system so described, is in all component states 
> simultaneously. AG  
> 
> S's cat scenario was not simply about the fate of a cat. After all, we 
> already knew a cat can't be alive and dead simultaneously. It must have been 
> to show the fallacy of the prevailing interpretation of superposition. AG 
> 
> Incidentally, as I pointed out in a previous discussion of this issue, 
> decoherence doesn't help. Even though it is extremely rapid, say 10^(-20) 
> sec, there is still a finite duration when, according to the standard 
> interpretation of superposition, the cat it is alive and dead simultaneously.

Once the cat is "alive and dead”, it is for life! (Grin). I mean that 
decoherence does not “collapse” the wave. It explains only why we can’t see it. 

By the linearity of evolution and of the tensor product, Once a superposition 
exist, it never disappear.



> LC might see this as nit-picking, but it isn't. We know a cat cannot be alive 
> and dead simultaneously regardless of the time duration, however short.

We don’t know that. A cat is dead + Alive in the same sense that a particle is 
going through two slits. With mechanism, there is no contradiction, as they are 
in different histories/computations.

Bruno


> So this result, when apply decoherence, doesn't avoid the superposition 
> fallacy illustrated by S's cat. It can be traced to the interpretation of the 
> superposition of (|decayed> + |undecayed>) of the radioactive source. AG
> 
> 
>> Also, I said I would get back to you about spin superpositions when I have 
>> time to research the issue. Other than those items, I honestly have no idea 
>> what you're complaining about. Try asking me again. AG 
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> 
> 
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Re: Something deeply hidden in the forest

On Tuesday, October 15, 2019 at 6:02:15 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:
>>
>> On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:
>>>
>>>
>>>
>>> On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell wrote:

 On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>
> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
> wrote:
>
>> On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:
>>>
>>> Part of the dislike of the MWI is that its proponents assume a 
>>> purity that is not an evident virtue of the intepretation.  For 
>>> example, 
>>> interpreting the squared amplitudes as probabilities seems to be 
>>> assumed, 
>>> along with the existence of the preferred basis in which the amplitudes 
>>> are 
>>> defined.  Together these are almost the same as CI.  If you ask 
>>> "probabilities of what?" in MWI the answer can't be probability of 
>>> existing 
>>> because MWI has committed to all solutions, however improbable, 
>>> existing.  
>>> So it becomes probability of finding yourself in a particular 
>>> world...which 
>>> depends on a theory of consciousness and seems to regress to von 
>>> Neumann 
>>> and Wigner.
>>>
>>> Zurek's envariance attempts to answer these questions and provide a 
>>> justification for preferred bases and what probability refers to.  But 
>>> notice that to the extent he succeeds he is justifying taking a simple 
>>> probabilistic view and saying one of those preferred states happens and 
>>> the 
>>> others don't.
>>>
>>> Brent
>>>
>>>
>>>
>> In the single-particle double-slit experiment*, an observer could see 
>> a dot appear anywhere on a screen where path interference does not 
>> reduce 
>> the probability to zero. So with the literal many-world-branching 
>> theory, 
>> how many different worlds are produced, each on with its own observer 
>> seeing a dot on the screen?
>>
>
> According to MWI, an infinite number. Each world will have the dot at 
> a different place on the screen.
>
> Bruce
>

 What you say may open up a bit of a hole or snag in MWI. This is 
 something I have been pondering some since Carroll's popularization. If 
 MWI 
 fundamentally preserves unitarity by splitting off worlds then 
 localization 
 of a measurement is an illusion.Consider a particle measured somewhere on 
 a 
 path from x and x'.  The path integral and the nonlocality of paths is a 
 sum over all possible measurements in all space containing x and x', then 
 there must be a continuum of possible worlds splitting off. If the 
 operator 
 has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
 continuum of possible worlds if there is indeed no fundamental 
 localization 
 with a measurement. This is not just infinite, but uncountably infinite.

 This is different from how decoherence maintains unitarity and 
 conserves qubits. There a local interaction occurs that induces quantum 
 phase to enter into a set of ancillary states or reservoir of states. Then 
 we can consider quantum states as finite, but unbounded from above, so 
 that 
 local observations and measurements are possible. 

 This does seem to run into some oddities that either need to be worked 
 out or that might indicate some gap in MWI. The persistence of nonlocality 
 in MWI is interesting for possible quantum gravitation work. In that case 
 I 
 can think of maybe a way around this, where this uncountably infinite set 
 of g_{ij} configurations, or Ψ[g_{ij}], can be identified with "exotic" 
 manifolds that are removed. It is less clear how this can happen with 
 ordinary quantum fields that have local realizations.

 LC

>>>
>>>
>>>
>>> To mix an analysis (or a theory) of the path integral with an analysis 
>>> (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
>>> that only leads to confusion.
>>>
>>> @philipthrift 
>>>
>>
>> I am thinking of a path integral as most physicists do, which is an 
>> action principle that is a sum over amplitudes or histories. You are 
>> thinking according to the quantum interpretation of Dowker and others, 
>> which has auxiliary postulates or assumptions.
>>
>> LC 
>>
>
> Path integrals or histories are  not eve brought up in Sean Carroll's book 
> (a search of the text shows).
>
> So they not present in any way in MWI.
>
> MWI (in Sean's mathematical formulation) is contrary to the path integral, 
> because histories (as you mention above) are simply not worlds (in Sean's 
> formulation).
>
> @philipthrift 
>

Also see Feynman's Meaning of Probabilities in QM paper.

But there are no

Re: Something deeply hidden in the forest



On Tuesday, October 15, 2019 at 5:48:58 AM UTC-5, Lawrence Crowell wrote:
>
> On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:
>>
>>
>>
>> On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell wrote:
>>>
>>> On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:

 On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
 wrote:

> On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:
>>
>> Part of the dislike of the MWI is that its proponents assume a purity 
>> that is not an evident virtue of the intepretation.  For example, 
>> interpreting the squared amplitudes as probabilities seems to be 
>> assumed, 
>> along with the existence of the preferred basis in which the amplitudes 
>> are 
>> defined.  Together these are almost the same as CI.  If you ask 
>> "probabilities of what?" in MWI the answer can't be probability of 
>> existing 
>> because MWI has committed to all solutions, however improbable, 
>> existing.  
>> So it becomes probability of finding yourself in a particular 
>> world...which 
>> depends on a theory of consciousness and seems to regress to von Neumann 
>> and Wigner.
>>
>> Zurek's envariance attempts to answer these questions and provide a 
>> justification for preferred bases and what probability refers to.  But 
>> notice that to the extent he succeeds he is justifying taking a simple 
>> probabilistic view and saying one of those preferred states happens and 
>> the 
>> others don't.
>>
>> Brent
>>
>>
>>
> In the single-particle double-slit experiment*, an observer could see 
> a dot appear anywhere on a screen where path interference does not reduce 
> the probability to zero. So with the literal many-world-branching theory, 
> how many different worlds are produced, each on with its own observer 
> seeing a dot on the screen?
>

 According to MWI, an infinite number. Each world will have the dot at a 
 different place on the screen.

 Bruce

>>>
>>> What you say may open up a bit of a hole or snag in MWI. This is 
>>> something I have been pondering some since Carroll's popularization. If MWI 
>>> fundamentally preserves unitarity by splitting off worlds then localization 
>>> of a measurement is an illusion.Consider a particle measured somewhere on a 
>>> path from x and x'.  The path integral and the nonlocality of paths is a 
>>> sum over all possible measurements in all space containing x and x', then 
>>> there must be a continuum of possible worlds splitting off. If the operator 
>>> has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
>>> continuum of possible worlds if there is indeed no fundamental localization 
>>> with a measurement. This is not just infinite, but uncountably infinite.
>>>
>>> This is different from how decoherence maintains unitarity and conserves 
>>> qubits. There a local interaction occurs that induces quantum phase to 
>>> enter into a set of ancillary states or reservoir of states. Then we can 
>>> consider quantum states as finite, but unbounded from above, so that local 
>>> observations and measurements are possible. 
>>>
>>> This does seem to run into some oddities that either need to be worked 
>>> out or that might indicate some gap in MWI. The persistence of nonlocality 
>>> in MWI is interesting for possible quantum gravitation work. In that case I 
>>> can think of maybe a way around this, where this uncountably infinite set 
>>> of g_{ij} configurations, or Ψ[g_{ij}], can be identified with "exotic" 
>>> manifolds that are removed. It is less clear how this can happen with 
>>> ordinary quantum fields that have local realizations.
>>>
>>> LC
>>>
>>
>>
>>
>> To mix an analysis (or a theory) of the path integral with an analysis 
>> (or a theory) of MWI is mixing two fundamentally contradictory frameworks 
>> that only leads to confusion.
>>
>> @philipthrift 
>>
>
> I am thinking of a path integral as most physicists do, which is an action 
> principle that is a sum over amplitudes or histories. You are thinking 
> according to the quantum interpretation of Dowker and others, which has 
> auxiliary postulates or assumptions.
>
> LC 
>

Path integrals or histories are  not eve brought up in Sean Carroll's book 
(a search of the text shows).

So they not present in any way in MWI.

MWI (in Sean's mathematical formulation) is contrary to the path integral, 
because histories (as you mention above) are simply not worlds (in Sean's 
formulation).

@philipthrift 

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Re: Something deeply hidden in the forest

On Tuesday, October 15, 2019 at 2:24:10 AM UTC-5, Philip Thrift wrote:
>
>
>
> On Monday, October 14, 2019 at 6:52:24 PM UTC-5, Lawrence Crowell wrote:
>>
>> On Monday, October 14, 2019 at 4:44:42 PM UTC-5, Bruce wrote:
>>>
>>> On Tue, Oct 15, 2019 at 5:38 AM Philip Thrift  
>>> wrote:
>>>
 On Monday, October 14, 2019 at 1:20:39 PM UTC-5, Brent wrote:
>
> Part of the dislike of the MWI is that its proponents assume a purity 
> that is not an evident virtue of the intepretation.  For example, 
> interpreting the squared amplitudes as probabilities seems to be assumed, 
> along with the existence of the preferred basis in which the amplitudes 
> are 
> defined.  Together these are almost the same as CI.  If you ask 
> "probabilities of what?" in MWI the answer can't be probability of 
> existing 
> because MWI has committed to all solutions, however improbable, existing. 
>  
> So it becomes probability of finding yourself in a particular 
> world...which 
> depends on a theory of consciousness and seems to regress to von Neumann 
> and Wigner.
>
> Zurek's envariance attempts to answer these questions and provide a 
> justification for preferred bases and what probability refers to.  But 
> notice that to the extent he succeeds he is justifying taking a simple 
> probabilistic view and saying one of those preferred states happens and 
> the 
> others don't.
>
> Brent
>
>
>
 In the single-particle double-slit experiment*, an observer could see a 
 dot appear anywhere on a screen where path interference does not reduce 
 the 
 probability to zero. So with the literal many-world-branching theory, how 
 many different worlds are produced, each on with its own observer seeing a 
 dot on the screen?

>>>
>>> According to MWI, an infinite number. Each world will have the dot at a 
>>> different place on the screen.
>>>
>>> Bruce
>>>
>>
>> What you say may open up a bit of a hole or snag in MWI. This is 
>> something I have been pondering some since Carroll's popularization. If MWI 
>> fundamentally preserves unitarity by splitting off worlds then localization 
>> of a measurement is an illusion.Consider a particle measured somewhere on a 
>> path from x and x'.  The path integral and the nonlocality of paths is a 
>> sum over all possible measurements in all space containing x and x', then 
>> there must be a continuum of possible worlds splitting off. If the operator 
>> has a continuum of eigenvalues *x*|x> = x|x> there must then be a 
>> continuum of possible worlds if there is indeed no fundamental localization 
>> with a measurement. This is not just infinite, but uncountably infinite.
>>
>> This is different from how decoherence maintains unitarity and conserves 
>> qubits. There a local interaction occurs that induces quantum phase to 
>> enter into a set of ancillary states or reservoir of states. Then we can 
>> consider quantum states as finite, but unbounded from above, so that local 
>> observations and measurements are possible. 
>>
>> This does seem to run into some oddities that either need to be worked 
>> out or that might indicate some gap in MWI. The persistence of nonlocality 
>> in MWI is interesting for possible quantum gravitation work. In that case I 
>> can think of maybe a way around this, where this uncountably infinite set 
>> of g_{ij} configurations, or Ψ[g_{ij}], can be identified with "exotic" 
>> manifolds that are removed. It is less clear how this can happen with 
>> ordinary quantum fields that have local realizations.
>>
>> LC
>>
>
>
>
> To mix an analysis (or a theory) of the path integral with an analysis (or 
> a theory) of MWI is mixing two fundamentally contradictory frameworks that 
> only leads to confusion.
>
> @philipthrift 
>

I am thinking of a path integral as most physicists do, which is an action 
principle that is a sum over amplitudes or histories. You are thinking 
according to the quantum interpretation of Dowker and others, which has 
auxiliary postulates or assumptions.

LC 

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Re: Something deeply hidden in the forest