> On 30 Nov 2018, at 12:29, agrayson2...@gmail.com wrote: > > > > On Friday, November 30, 2018 at 9:03:51 AM UTC, Bruno Marchal wrote: > >> On 28 Nov 2018, at 15:02, agrays...@gmail.com <javascript:> wrote: >> >> >> >> On Wednesday, November 28, 2018 at 1:41:03 PM UTC, Bruno Marchal wrote: >> >>> On 26 Nov 2018, at 22:43, agrays...@gmail.com <> wrote: >>> >>> >>> >>> On Monday, November 26, 2018 at 4:41:42 PM UTC, agrays...@gmail.com >>> <http://gmail.com/> wrote: >>> >>> >>> On Monday, November 26, 2018 at 12:01:05 PM UTC, Bruno Marchal wrote: >>> >>>> On 23 Nov 2018, at 13:30, agrays...@gmail.com <> wrote: >>>> >>>> >>>> >>>> On Friday, November 23, 2018 at 11:29:14 AM UTC, Bruno Marchal wrote: >>>> >>>>> On 21 Nov 2018, at 18:03, agrays...@gmail.com <> wrote: >>>>> >>>>> >>>>> >>>>> On Monday, November 19, 2018 at 3:52:37 PM UTC, Bruno Marchal wrote: >>>>> >>>>>> On 18 Nov 2018, at 14:00, agrays...@gmail.com <> wrote: >>>>>> >>>>>> >>>>>> >>>>>> On Sunday, November 18, 2018 at 12:19:20 PM UTC, Bruno Marchal wrote: >>>>>> >>>>>>> On 16 Nov 2018, at 15:38, agrays...@gmail.com <> wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Friday, November 16, 2018 at 10:14:32 AM UTC, scerir wrote: >>>>>>> >>>>>>> >>>>>>>> Il 16 novembre 2018 alle 10.19 agrays...@gmail.com <> ha scritto: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Thursday, November 15, 2018 at 2:14:48 PM UTC, scerir wrote: >>>>>>>> >>>>>>>> >>>>>>>>> Il 15 novembre 2018 alle 14.29 agrays...@gmail.com <> ha scritto: >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Thursday, November 15, 2018 at 8:04:53 AM UTC, scerir wrote: >>>>>>>>> Imagine a spin-1/2 particle described by the state psi = sqrt(1/2) >>>>>>>>> [(s+)_z + (s-)_z] . >>>>>>>>> >>>>>>>>> If the x-component of spin is measured by passing the spin-1/2 >>>>>>>>> particle through a Stern-Gerlach with its field oriented along the >>>>>>>>> x-axis, the particle will ALWAYS emerge 'up'. >>>>>>>>> >>>>>>>>> >>>>>>>>> Why? Won't the measured value be along the x axis in both >>>>>>>>> directions, in effect Up or Dn? AG >>>>>>>> "Hence we must conclude that the system described by the |+>x state is >>>>>>>> not the >>>>>>>> same as a mixture of atoms in the |+> and !-> states. This means that >>>>>>>> each atom in the >>>>>>>> beam is in a state that itself is a combination of the |+> and |-> >>>>>>>> states. A superposition >>>>>>>> state is often called a coherent superposition since the relative >>>>>>>> phase of the two terms is >>>>>>>> important." >>>>>>>> >>>>>>>> .see pages 18-19 here https://tinyurl.com/ybm56whu >>>>>>>> <https://tinyurl.com/ybm56whu> >>>>>>>> >>>>>>>> Try answering in your own words. When the SG device is oriented along >>>>>>>> the x axis, now effectively the z-axix IIUC, and we're dealing with >>>>>>>> superpositions, the outcomes will be 50-50 plus and minus. Therefore, >>>>>>>> unless I am making some error, what you stated above is incorrect. AG >>>>>>> sqrt(1/2) [(s+)_z +(s-)_z] is a superposition, but since sqrt(1/2) >>>>>>> [(s+)_z +(s-)_z] = (s+)_x the particle will always emerge 'up' >>>>>>> >>>>>>> >>>>>>> I'll probably get back to on the foregoing. In the meantime, consider >>>>>>> this; I claim one can never MEASURE Up + Dn or Up - Dn with a SG >>>>>>> apparatus regardless of how many other instruments one uses to create a >>>>>>> composite measuring apparatus (Bruno's claim IIUC). The reason is >>>>>>> simple. We know that the spin operator >>>>>> >>>>>> Which one? >>>>>> >>>>>> Good question. AG >>>>>> >>>>>> There are spin operator for each direction in space. The superposition >>>>>> of up and down is a precise pure state, with precise eigenvalues, when >>>>>> measuring state in the complementary directions. >>>>>> >>>>>> As I wrote earlier, based on scerir's superpositions on different axes, >>>>>> and simulation, I now think that Up + Dn and Up - Dn can be measured >>>>>> along the x axis but not along the z axis (which I was focused on). >>>>> >>>>> All you need to do is a change of base. The operator will be defined >>>>> clearly by the Eigen value on the diagonal in the corresponding base. You >>>>> can prepare any state, and measure them “in any base”. >>>>> >>>>> I'll get back to this issue in my next post. AG >>>>>> You were probably correct about x axis measurements, but perhaps were >>>>>> not clear enough. You were not explicit that measurements along the x >>>>>> axis is a different SG experiment from along z axis. >>>>> >>>>> OK. Sorry. >>>>>> I thought you meant do them in succession, not as separate experiments. >>>>> >>>>> Ah? OK. >>>>>> Also introducing an infinity of universes seems extraneous and confusing >>>>>> for a solution to this problem. AG >>>>> I are probably different on this. I don’t take the word “universe” too >>>>> much seriously, as with mechanism we know at the start that there is >>>>> “physical universe” at all, just the natural numbers with the laws of >>>>> addition and multiplication. Both the computational and the quantum state >>>>> are relative, and high level, pertaining to what is “observable” for some >>>>> the point of view of some locally finite subject, run by some computation. >>>>> >>>>> The empirical point, though, is that to predict correctly an event in >>>>> quantum mechanics, we have to take into account may simultaneous >>>>> “incompatible path”, like going through each hole in a plane. Quantum >>>>> computations, for example, exploits that seemingly parallelism. >>>>> >>>>> I don't like this approach -- in fact I abhor it -- since it implies >>>>> simultaneous interference among a multitude of paths to the same point on >>>>> the detection screen. This adds an unnecessary mystery to QM. In the >>>>> Hilbert Space representation, the wf is what it is, but can be >>>>> represented in a multitude of different bases. It is therefore misleading >>>>> to claim the system being analyzed is in a multitude of states; rather it >>>>> is in one state, which due to linear algebra, has many representations. AG >>>> >>>> >>>> I can be OK with this, if you agree that the consciousness of the observer >>>> is relatively associated to those representations, in the base “chosen” by >>>> nature in the evolution of the brain. That gives rise to the “relative >>>> state” view of QM. >>>> >>>> I don't agree. I am not even sure what you mean. You don't need a >>>> conscious observer to detect the results of a slit experiment. >>> >>> Did I say that? >>> >>> IMO yes. You asserted the need for an observer. The interference pattern >>> exists if there are no observers. It's like saying the Moon exists even if >>> no one ever looks at it, which was the situation throughout most of the >>> Moon's lifetime. AG >>> >>> >>> >>>> All you need is a detector to record the results. Feynman made this point >>>> and I don't see anything problem with this logic. >>> I agree with Feynman and Everett on this. It is the advantage of NOT >>> believing in the wave reduction: consciousness is entirely handle by the >>> Mechanist theory of mind. But then we can associate consciousness to the >>> apprehension of the distinction brought by the measuring apparatus, in all >>> branches of the superposition, and you get the “many-worlds” or the >>> “many-relative-histories”. >>> >>> Where in Feynman's postulates does he assert or infer no wave packet >>> reduction? I have to check his postulates, but if he really developed a >>> particle-only theory, there are no wave packets. AG >>>> The problem IMO with sums over histories is that it adds a superfluous >>>> mystery (in spades) to the results, say, of a slit experiment. We still >>>> have the mystery as to why interference for every point along the screen >>>> in a single trial, yields a single impact. But with sums over histories >>>> IIUC, for each impact point or result, we also have an infinite set of >>>> histories which the particle is in simultaneously. I don't see that >>>> anything has been gained, other than having an additional baffling mystery >>>> used to sell books which confuse the lay public as well as professional >>>> physicists. AG >>> >>> It is just QM without reduction of the wave packet. If there is no wave >>> packet reduction, you get the relative states, including consciousness >>> differentiation, using just the mechanist theory of mind (the oldest theory >>> of mind). >>> >>> You're reading much too much into Sums Over Histories (or Relative Dtates) >>> to reach this conclusion. CMIIAW, but Feynman discovered another way to >>> calculate probabilities. He didn't, and couldn't explain why we get one >>> result and not another in, say, a slit experiment. At best he was neutral >>> as to what happens to the wf at measurement time, since, IIUC, he has no >>> wf's in his theory. AG >>> >>> I checked the postulates in Feynman's Sums Over Histories (in link provided >>> by Phil) and I see nothing related to waves, as expected, and thus nothing >>> about collapse of anything. >> >> >> You can derive Schroedinger's equation (even Dirac’s equation) from >> Feynman’s formulation. This should be intuitively obvious if you read >> Feynman popular book on the Nature of Light. >> >> Not at all obvious. Do you have a link which proves that? AG >> > > > It is common knowledge in quantum field theory. PBS promised to make a video > on this. I studied this in the book by Feyman and Hibbs (QM and Path > Integral). > > > >> The waves are there. >> >> Was that before or after Feynman disavowed his belief that QM can be derived >> totally using particles? AG > > I don’t know. > > > >> >> But yes: the collapse does not make sense in Feynman’s formulation (or it >> looks even more ad hoc and non covariant). That is a reason to disbelieve in >> the collapse, but then you get some version of the many-world view (which >> you dislike apparently). >> >> MW is too extravagant to be true, > > Why? Why would be that extravagant? > > MW is the most extravagant theory possible and you just can't see it? Take > your head out of the ground and report back. AG
Again, why is it extravagant. I predicted this well before I even knew the term “quantum”, when I discovered that arithmetic emulates all computations (and my only doubt at that time was about “Church’s thesis”, without which “computable” seems to remain an epistemic relative notion). > > > Nature loves to do many things, like the water molecules in the Ocean. In > this list, most people agree than many things is conceptually simpler than > one particular thing. > > Except for one little thing; you can't explain the processes by which these > worlds are created! You might think studying the theory before criticising it. I have no clues at all why you are saying this, except by referring to the usual current metaphysical prejudices. > It's really very silly IMO. AG You need to argue. > > >> and moreover, even its advocates like you cannot say what another world >> includes. > > > ? > > You said it earlier in slightly different words. You have no idea how another > world is created or what's in it. I think we've departed from any reality > thinking when it comes to MW. AG Mechanism and elementary arithmetic is enough. >> Go back to Bruce's horse race example to see what happens to Schrodinger's >> equation when the measurement occurs. AG > > ? You might develop a little bit. With the MW, a measurement is only an > interaction. > > Reliance on rhetoric won't help. AG ? Bruno > > > > >> >> >> >> >>> I would suppose the same applies to Heisenberg's Matrix Mechanics; no >>> waves, no collapse. >> >> Those are equivalent theories. Deustch defended the MW, even its locality, >> in the context of the Heisenberg Matrix formulation. The theories here are >> all equivalent (unless they populate some collapse). >> >>> I suppose you could say they just produce correct probabilities, and imply >>> nothing about relative states other than their probabilities (which wave >>> mechanics does), but certainly nothing about consciousness. >> >> OK. (In my approach I derive the MW and its quantum formalism from the >> natural numbers and the laws of addition and multiplication, and nothing >> else, except at the meta-level I use the mechanist hypothesis to make sense >> of this, but it is a very weak assumptions which can be weaken even more). >> >> Sorry, but I don't believe that is possible. AG > > Then you will be astonished, because with Mechanism, there is no other > solution available, unless adding some “magic” to computaionalism, which > makes no sense. > > Bruno > > > > > >>> To summarize: you're right that they are "no collapse" theories, but IMO >>> they say nothing about consciousness. AG >> >> Well, with mechanism (that you can see as a theory of consciousness) there >> is no collapse indeed. But the quantum aspect of nature is explained from >> that theory of consciousness, not the inverse. Usually it is those who >> believe in the collapse who mix quantum and consciousness, like Wigner, von >> Neuman, Walker, etc. With mechanism, a measurement is only an interaction, >> locally irreversible (due to big numbers, not to any physical indeterminacy). >> >> Bruno >> >> >> >> >> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>> >>>>>>> has exactly two eigenstates, each with probability of .5. We can write >>>>>>> them down. We also know that every quantum measurement gives up an >>>>>>> eigenvalue of some eigenstate. Therefore, if there existed an Up + Dn >>>>>>> or Up - Dn eigenstate, it would have to have probability ZERO since the >>>>>>> Up and Dn eigenstates have probabilities which sum to unity. Do you >>>>>>> agree or not, and if not, why? TIA, AG >>>>>> >>>>>> You add the probabilities, but you need to add the amplitudes of >>>>>> probabilities instead, and then take their square. You simply dismiss >>>>>> the quantum formalism, it seems to me. >>>>>> >>>>>> I did not; an incorrect inference on your part. >>>>> All right. (I was just trying to figure out what you did, to be sure). >>>>>> I never mentioned Born's rule (it wasn't necessary), >>>>> >>>>> You did use the probability 1/2 at some place, with the particle in a >>>>> state 1/sqrt(2)(up + down). We use all the time the Born rule when we >>>>> talk about measurement. >>>>> >>>>> I just assumed a probability of .5 for Up and Dn states after application >>>>> of Born's rule. AG >>>> >>>> That was my point. >>>> >>>> Your point, IIUC, was that I was denying the postulates of QM by ignoring >>>> Born's Rule, but I was not doing that. I just chose not to mention it. >>>> Nothing more. AG >>> >>> OK, then. >>> >>> Bruno >>> >>> >>> >>>> >>>> Bruno >>>> >>>> PS I got a mail back as undelivered. I will try to resend it later. >>>> >>>> >>>> >>>>> >>>>>> from which one cannot infer I am criticizing QM itself. AG >>>>> >>>>> I am just trying to understand what you don’t understand, which is not >>>>> easy in a context where the more we understand the formalism, the less we >>>>> understand what it could mean, even more so if we give sense to a dualist >>>>> wave packet reduction. >>>>> >>>>> I am a logician: it is clear that Copenhagen and Everett are not two >>>>> different interpretations, but two different theories. One is >>>>> Schroedinger equation + wave packet reduction + a dualist theory of >>>>> mind/observation), the other is just Schroedinger equation only + the >>>>> “usual” mechanist theory of mind. There are many possible debate on all >>>>> his of course. >>>>> >>>>> I urge you to study the treatment of the interferometer in David Albert >>>>> books. It is weird. Bohr is right on this: to understand it means to get >>>>> the point that is hard to figure out how nature could to that, but from >>>>> the mechanist post Gödel view, it is rather natural, as we observe is >>>>> given by a statistics on infinitely many computations/histories. >>>>> >>>>> Bruno >>>>> >>>>> >>>>> >>>>> >>>>>> >>>>>> The states constituted a vector space: the sum (superposition) of >>>>>> orthogonal states are pure state, after a change of base, and I did give >>>>>> you the corresponding operator. You are not criticising an >>>>>> interpretation of QM, but QM itself. >>>>>> >>>>>> >>>>>> Bruno >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>> In fact (s+)_z = sqrt(1/2) [(s+)_x + (s-)_x] >>>>>>>>> >>>>>>>>> and (s-)_z = sqrt(1/2) [(s+)_x - (s-)_x] >>>>>>>>> >>>>>>>>> (where _z, _x, are the z-component and the x-component of spin) >>>>>>>>> >>>>>>>>> so that psi = sqrt(1/2)[(s+)_z +(s-)_z] = (s+)_x. (pure state, not >>>>>>>>> mixture state).. >>>>>>>>> >>>>>>>>> AGrayson2000 asked "If a system is in a superposition of states, >>>>>>>>> whatever value measured, will be repeated if the same system is >>>>>>>>> repeatedly measured. But what happens if the system is in a mixed >>>>>>>>> state?" >>>>>>>>> >>>>>>>>> Does Everett's "relative state interpretation" show how to interpret >>>>>>>>> a real superposition (like the above, in which the particle will >>>>>>>>> always emerge 'up') and how to interpret a mixture (in which the >>>>>>>>> particle will emerge 50% 'up' or 50% 'down')? >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> -- >>>>>>>>> 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-li...@googlegroups.com <>. >>>>>>>>> To post to this group, send email to everyth...@googlegroups.com <>. >>>>>>>>> Visit this group at https://groups.google.com/group/everything-list >>>>>>>>> <https://groups.google.com/group/everything-list>. >>>>>>>>> For more options, visit https://groups.google.com/d/optout >>>>>>>>> <https://groups.google.com/d/optout>. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> -- >>>>>>>> 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-li...@googlegroups.com <>. >>>>>>>> To post to this group, send email to everyth...@googlegroups.com <>. >>>>>>>> Visit this group at https://groups.google.com/group/everything-list >>>>>>>> <https://groups.google.com/group/everything-list>. >>>>>>>> For more options, visit https://groups.google.com/d/optout >>>>>>>> <https://groups.google.com/d/optout>. >>>>>>> >>>>>>> >>>>>>> -- >>>>>>> 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-li...@googlegroups.com <>. >>>>>>> To post to this group, send email to everyth...@googlegroups.com <>. >>>>>>> Visit this group at https://groups.google.com/group/everything-list >>>>>>> <https://groups.google.com/group/everything-list>. >>>>>>> For more options, visit https://groups.google.com/d/optout >>>>>>> <https://groups.google.com/d/optout>. >>>>>> >>>>>> >>>>>> -- >>>>>> 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-li...@googlegroups.com <>. >>>>>> To post to this group, send email to everyth...@googlegroups.com <>. >>>>>> Visit this group at https://groups.google.com/group/everything-list >>>>>> <https://groups.google.com/group/everything-list>. >>>>>> For more options, visit https://groups.google.com/d/optout >>>>>> <https://groups.google.com/d/optout>. >>>>> >>>>> >>>>> -- >>>>> 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-li...@googlegroups.com <>. >>>>> To post to this group, send email to everyth...@googlegroups.com <>. >>>>> Visit this group at https://groups.google.com/group/everything-list >>>>> <https://groups.google.com/group/everything-list>. >>>>> For more options, visit https://groups.google.com/d/optout >>>>> <https://groups.google.com/d/optout>. >>>> >>>> >>>> -- >>>> 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-li...@googlegroups.com <>. >>>> To post to this group, send email to everyth...@googlegroups.com <>. >>>> Visit this group at https://groups.google.com/group/everything-list >>>> <https://groups.google.com/group/everything-list>. >>>> For more options, visit https://groups.google.com/d/optout >>>> <https://groups.google.com/d/optout>. >>> >>> >>> -- >>> 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-li...@googlegroups.com <>. >>> To post to this group, send email to everyth...@googlegroups.com <>. >>> Visit this group at https://groups.google.com/group/everything-list >>> <https://groups.google.com/group/everything-list>. >>> For more options, visit https://groups.google.com/d/optout >>> <https://groups.google.com/d/optout>. >> >> >> -- >> 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-li...@googlegroups.com <javascript:>. >> To post to this group, send email to everyth...@googlegroups.com >> <javascript:>. >> Visit this group at https://groups.google.com/group/everything-list >> <https://groups.google.com/group/everything-list>. >> For more options, visit https://groups.google.com/d/optout >> <https://groups.google.com/d/optout>. > > > -- > 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 > <mailto:everything-list+unsubscr...@googlegroups.com>. > To post to this group, send email to everything-list@googlegroups.com > <mailto:everything-list@googlegroups.com>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
