On 4/20/2022 5:53 PM, Bruce Kellett wrote:
On Thu, Apr 21, 2022 at 10:05 AM George Kahrimanis <[email protected]> wrote:On Tue, Apr 19, 2022 at 11:09 AM Brent Meeker <[email protected]> wrote: The only purpose of the box in Schroedinger's thought experiment was to put off the observers perception. Really the thought experiment is over when the radioactive decay occurs. That atom has transitioned to a different nuclear state which is entangled with and recorded in the environment. On Tuesday, April 19, 2022 at 4:20:49 AM UTC+3 Bruce wrote: Yes. Schrodinger had the cat in a box to emphasize the idea that the cat was in a macro-superposition of alive/dead. This misled Wigner to the extent that he thought the state collapsed only when the box was opened. All of this was made redundant when it was realized that decoherence rendered the state definite almost instantaneously. Saibal makes the same mistake when he claims that Alice, after her measurement, is still in a superposition until Bob sees her result. The idea that the superposition still exists since decoherence is only FAPP is something of a red herring -- in MWI, Alice has branched according to her result into up and down branches that no longer interfere. There is no macro-superposition. -1- Decoherence (by a chaotic environment) turns an entangled superposition into a non-coherent density matrix, only if we subsequently omit the environment from the description of the system. (Not if we keep the environment in the description.)FAPP is for a reason -- we automatically trace out unneeded environmental variables.-2- The "box" (in which Scroedinger's cat is enclosed, with the lethal apparatus) contains also its "environment", so a quantum descrition of this box describes the environment also. Therefore I do not agree that decoherence INSIDE THE BOX will ruin the superposition ASSESSED FROM OUTSIDE THE BOX. So, Wigner was right. I suppose that Saibal also is right, though I have not checked that message (sorry).Unfortunately for this idea, decoherence does not stop at the box. In the time that Wigner thinks about this before he opens the box, decoherence has enveloped essentially the whole world, so Wigner himself has decohered into either a world with a dead cat or a world with a live cat. He can't dissociate himself from the split that occurs, so from his point of view outside the box, the superposition is long gone, and he has to deal with a simple classical state of either a dead cat or a live cat -- no superposition remains.
Superposition or pure wave-function is a matter of basis. We say no superposition remains because we can only measure in a few classically stable dimensions: alive/dead here/there ... But exactly why this is the case is known as "the basis" problem. It's not obvious from the Schroedinger equation, as MWI advocates are wont to pretend.
Brent
I rephrase my conclusion. I agree with you, on the splits being technically non-local, but this is only an artifact of describing the dynamical evolution of the wavefunction in space-like slices forming a time-like stack. Thus a split affects the whole slice in which it occurs. But seen from a moving train, it would be a different slice! Only on and inside the light cone, the split is physically meaningful. The split is associated with the light cone, so it is Lorentz invariant. Thanks to your insistence, now I see the difference between non-local HV theories, which violate relativity, and MWI, which does not.I had always made a distinction between faster-than-light influences, which are intrinsically local since they involve the local transfer of information via some medium (albeit FTL), and non-local influences, which do not involve any FTL transfers. They are instantaneous and non-local. So that does not violate relativity. In fact, FTL transmission does not strictly violate relativity either -- tachyons are perfectly consistent with relativity. All that relativity forbids is the acceleration of a subluminal particle to the speed of light and beyond. Tachyons are always superluminal, so are not forbidden. The various no-signalling theorems demonstrate that Bell-type correlations, while non-local, do not involve FTL signalling or tachyonsBruce I am writing in a hurry, because these days are hectic. I may have missed some important postings, sorry. I would welcome any hints (with the name and time of posting) sent to my G-mailbox: GeKahrim. George K. --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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLQRTYQS09Dn7JVMF2k%2BaADoJqXonr_GCvkNk-0uc__3bw%40mail.gmail.com <https://groups.google.com/d/msgid/everything-list/CAFxXSLQRTYQS09Dn7JVMF2k%2BaADoJqXonr_GCvkNk-0uc__3bw%40mail.gmail.com?utm_medium=email&utm_source=footer>.
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