> On 13 Aug 2018, at 00:48, Bruce Kellett <[email protected]> wrote: > > From: Bruno Marchal <[email protected] <mailto:[email protected]>> >>> On 11 Aug 2018, at 02:49, Bruce Kellett <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> From: Bruno Marchal <[email protected] <mailto:[email protected]>> >>>> On 9 Aug 2018, at 14:03, Bruce Kellett <[email protected] >>>> <mailto:[email protected]>> wrote: >>>>> >>>>>> Without collapse and FTL potential, or FTL (non-local) hidden variable >>>>>> theory, how do you interpret the singlet state? >>>>> >>>>> That is actually a rather strange question. How do you think I might >>>>> interpret the singlet state? I think that I have been talking about it >>>>> here for long enough for you to have worked it out. The singlet state is >>>>> a non-separable state that is symmetric under rotations about the axis >>>>> between the particles. However, that symmetry will generally be broken by >>>>> any interaction with one or other of the constituent particles. >>>> >>>> But it is here that I suspect you introduce some collapse. >>> >>> The interaction with one particle reduces the symmetry of the non-separable >>> state so that it becomes separable. >> >> Locally, and from the observer viewpoint, not in the big picture, as nothing >> is ever reduced. The superposition does not disappear. > > There is still a superposition, even though it has decohered and the separate > results are in FAPP orthogonal branches. But the superposition is not the > issue -- that relevant fact is that the measurement has destroyed the > rotational symmetry of the state. > > >>> You might call this a "collapse" if you wish, but this is an >>> epistemological collapse, not an ontological one. It is the nature of the >>> state representing one's knowledge that changes (the old state "collapses" >>> with the advent of new knowledge). >> >> Then I agree. That makes things local, and personal somehow. You get close >> to “my” version of the many-mind account. > > I doubt it. There is no "bigger picture" in which the symmetry is preserved. > > >>> But that is purely epistemological, and does not involve any FTL >>> information transfer. >> >> That’s my point. > > But you apparently still do not accept that the symmetry of the state is > destroyed, even without physical FTL.
The destruction is only in the mind of the observer, like the WM-duplication is symmetrical for an outsider, but non symmetrical for the experiencer. > The wave function is not a "physical" object -- it can easily change > instantaneously, just as probabilities change on the advent of new > information. Then we are no more in Everett non-collapse QM, and I am not sure how you can explain the double slit or spin polarisation without a physical wave. > >>> It is just as if the probability that your horse will win the race >>> "collapses" when you find out, after the race has been run, that it came >>> last! >>> >>>>> In particular, the symmetry is broken by the imposition of a directional >>>>> magnetic field, as in a Stern-Gerlach magnet used to measure the spin >>>>> component of one of the particles in the direct defined by that external >>>>> magnetic field. >>>>> >>>>> The singlet is strongly non-separable, so this external interaction with >>>>> one of the constituents is instantaneously felt by the other component >>>>> particle. >>>> >>>> How could this be verified? >>> >>> It is verified by the Freedman-Clauser and Aspect experiments (and many >>> other more recent experiments). >> >> This tests only the non separability issue. Not the existence of a physical >> FTL in our branch. That follows from what you say above. > > The non-separability is the non-locality. Do you not yet understand that? Yes. I do understand that, and I prefer to use non-separability. “Non-locality” is ambiguous, because many are using that term for FTL influence (even if no transfer of information is involved). > > >>>> Any verification possible will need further interaction, and we can see >>>> only the branche of the universe our own result have spread on. >>> >>> The verification comes from the results of remote experiments -- and those >>> results do not change during the time it takes for the experimenters to >>> come together to compare findings. >> >> Those results makes just Alice and Bob knowing which branches they belong >> too. The non-locality is a global notion on the full wave/multiverse, > > That has never been demonstrated. It is a pious hope of yours, but you always > shy away from proving it. If you believe in FTL, you are the one who should prove that remarkable fact. It follows indeed from all collapse theories, but not for the MW. > > >> but the FTL are needed only if we associate the mind on Bob and Alice to the >> same branche, which has no meaning for me once they are space separated. > > You might not accept that they can be in the same branch, but that does not > mean that it is not a proven fact. If they are space separated, I am not sure I can make sense of being in the same branch. > > >> But we know we disagree on how to interpret the singlet state in the MW >> frame. >> >>>>> That non-local influence is the essence of the non-separability of the >>>>> state -- it is a unit, and any interaction with a part is an interaction >>>>> with the whole. >>>> >>>> That looks magical to me, and as I said, I am not sure this can be >>>> verified. Aspect-like experiment do not verify this for sure. >>> >>> It might look magical to you, but that is because you have not really >>> accepted the true weirdness of quantum theory. The Aspect-like experiments >>> certainly do verify this -- why else do you think that these experiments >>> were performed? >> >> To verify QM’s prediction. After Aspect, the choice is between >> determinacy+locality+many-worlds or one world + 3p indeterminacy, 3p >> physical FTL. > > Determinism has nothing to do with it. Aspect and Bell rule out deterministic > local theories, so non-locality is the only possibility. Many-worlds does not > change that. Determinism is the issue. In a collapse theory, you need indeterminism to assure the non signalling FTL of information. But you have still some physical FTL/simultaneous action. With the MW, the situation is entirely deterministic and there is no need of any FTL. > Both Bell's theorem and Aspect's results are true in many-worlds as in any > other interpretation of QM. Of course. > Don't you understand that that is why most commentators from the many-worlds > perspective try to show that Bell's theorem does not apply to many worlds? They are wrong. Bell’s violation is necessary in all branches. But what happens is that if one branch is selected, by collapse or by hidden variables, then *that* transform the non-locality (Bell’s violation) into FTL. Without collapse, we don’t need hidden variables, nor any FTL, to explain the non-locality and why it never disappears. > They know that if it does, then many-worlds is as non-local as any other > interpretation. But without FTL physical actions, so MW is covariant, unlike hidden variable theory, or wave-collapse theory. > Of course, they fail in their attempts to deflect Bell's result. In fact, > some of the attempts and failures are almost farcical in their silliness, but > I suppose you can't see that, either. ? Bruno > > Bruce > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > 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 [email protected]. To post to this group, send email to [email protected]. 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