On Wed, Nov 27, 2024 at 4:42 AM smitra <[email protected]> wrote: > On 25-11-2024 23:21, Bruce Kellett wrote: > > On Tue, Nov 26, 2024 at 12:16 AM smitra <[email protected]> wrote: > > > >> On 24-11-2024 05:04, Bruce Kellett wrote: > >> > >>> If QM were intrinsically local, then you would be able to give this > >>> local account of the correlations. > >>> You are manifestly unable to do this. > >> > >> It's obvious from the time evolution specified by the local > Hamiltonian. > > > > You have tried this approach before. You seem unable to realize that > > that is just a restatement of your position. And it is that position > > that is in question. Restating your conclusion is not an argument or > > an account of anything. > > > > You are disputing a triviality, namely that we have a unitary time > evolution specified by a local Hamiltonian: > > U(t) = exp(-i H t/hbar) > > At least that's what you are claiming. What you are really doing is that > you play hide and seek in the complexity of this. Your real bone is, of > course, with the idea that time evolution is unitary and that there is > no collapse. Obviously, the only plausible reason QM could be non-local > is if there is a real collapse. If everything always stays unitary with > the unitary transform specified by a local Hamiltonian then there is no > collapse, and everything always stays local. That doesn't mean that you > can't have states with non-local properties, what it means is that > whatever happens always follows from applying local laws. Sol, non-local > features can be explained using common cause effects propagated by local > unitary dynamics. >
You appear to be veering towards the position exemplified by Wallace in his book "The Emergent Multiverse", where he says that in Everettian quantum mechanics interactions are local, but states are nonlocal (p. 310). If you do take such a position, you have to acknowledge the importance of the nonlocality of the entangled state. Going on about unitary dynamics is of no help to you in understanding this. > >> You made the extraordinary claim that Bell proved that QM > >> is non-local, which is plain nonsense. > No, it is not nonsense. Bell's theorem, which depends only on the assumption of locality, shows that the correlations from entangled particles must satisfy certain inequalities. These inequalities are violated by standard quantum mechanics, and also by experiment. The challenge is to explain these violations. And that is possible only by invoking nonlocality. If you think you can explain the experiments without invoking nonlocality, go ahead. But no one has ever done this. > Yes, it invokes unitary QM with the unitary time evolution specified by > a local Hamiltonian. This implies a MWI scenario, but not per se with > all the baggage of splitting worlds that are supposed to split in > independent ways. You end up with different sectors that are entangled. > So, you are invoking the nonlocality of states that Wallce refers to. That is all very well, but that is not a detailed explanation of how this works. Wallace can't give a detailed explanation either, because that would involve nonlocal dynamics, but he thinks many-worlds allows you to avoid this. He is mistaken, of course. Bell's theorem doesn't prove that QM is non-local. If that were the > case, then this would be just another of QM that would be proven in any > QM textbook, and it would make unitary QM specified by a local > Hamiltonian inconsistent. The whole debate about e.g. black hole > information loss wouldn't happen in that case. The fact that this is a > hot topic in theoretical physics proves that you > don't really understand the subject matter you are debating here. It's > true that QM could be non-local but that's not implied by Bell's > theorem. If you were right on this point, then that would imply that all > theoretical physicists get this wrong and you are one of the few people > who knows better. So, clearly not a matter of "Not everyone gets it > right", rather that everyone else but you is getting it wrong, and that > makes it appropriate to invoke an argument from authority pointing that > out. > You are talking a lot of nonsense. I refer you to a paper by Brunner *et al.*, Rev Mod. Phys. 86 (2014) pp.419-478. This is also available at arxiv.org/abs/1303.2849 The abstract states "Bell's 1964 theorem, which states that the predictions of quantum theory cannot be accounted for by any local theory, represents one of the most profound developments in the foundations of physics." Brunner *et al.* go on to derive the CHSH (Clauer-Horne-Shimony-Holt) inequality using only local dynamics, and prove that this inequality is violated in conventional QM, as well as in many experiments. This proves that quantum mechanics is intrinsically nonlocal. (If you like, it demonstrates that nonlocal states are intrinsic to the theory.) And b.t.w. if there is a Bell's theorem purely about unitary QM that > doesn't invoke hidden variables, you could just state it right here. I don't prove Bell's theorem here, but I have referred you to Bell's original papers, and also to the review article by Brunner et al., above. If you actually do the research for yourself, you can see that many authors agree with what I have been saying. You are the one that is out on a limb. You > didn't do that and made the counterclaim against me when I pointed out > that Bell's theorem is about inequalities for certain correlations > satisfied by local hidden variable theories, which is common knowledge. > No according to the original sources: hidden variables do not come into it. And I made the remark that it's then a theorem about local hidden > variable theories, not QM, so it's relevance to QM is limited to the > ideas that QM might have an underlying hidden variable theory. You are > disputing this only on your say so, so basically an argument from > authority where the authority is you, not even references to the works > other experts in the field. > I have given you references here, and I have referred you to Bell's original papers before.. But you do talk an awful lot of nonsense. 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]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAFxXSLRh9jBW9GpkR2CVE%2BF4iDri%2Bmb7e7DHsSLGJb-PStja8Q%40mail.gmail.com.
