On Thu, Oct 3, 2019 at 7:08 PM Bruno Marchal <marc...@ulb.ac.be> wrote:
> > On 1 Oct 2019, at 19:37, 'Brent Meeker' via Everything List < > everything-list@googlegroups.com> wrote: > > On 10/1/2019 4:38 AM, Bruno Marchal wrote: > >> Right. Then the non locality has disappeared from the wave equation at > the start. > > > > No, Bruce's point is that it must be present at the start. Otherwise > Bell's inequality couldn't be violated. > > Bruce agree that there is no FTL action, that is locality. The non > locality is in the perspective view. It is not a global truth, as that is > obvious if you agree that the wave function evolution is only a rotation in > some space. Rotation are typically local, even in abstract spaces (which in > Everett and with mechanism are the real thing). > Now, with “one physical universe”, that non-local perspective implies some > FTL action. > I think you have missed the point, Bruno. The wave function itself is non-local. Consider the entangled singlet state that we have been talking about: |psi> = (|+>|-> - |->|+>)/sqrt(2). The kets in the tensor product refer to different particles, with arbitrary separation in space-time. But this is a single state. Because it is non-separable, and refers to different spacetime locations, it is intrinsically non-local. You can rotate it as much as you like in Hilbert space, but you will never remove the non-locality. That is the way it is -- it will always refer inevitably to two separate spacetime locations. As Wallace reports Deutsch to have said: "quantum theory is a theory of local interactions with non-local states." So with EPR correlations, the state is intrinsically non-local but all the measurement interactions are local. The trouble is that, because of Bell's theorem, there is no local causal explanation of the correlations -- they are evidence of the non-locality of the state. And there is no FTL action -- that would be a local hidden variable causal explanation, and Bell rules that out. 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 everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLSewE7FaznrJTY6OeQO240hqKX4DSm6rW1743PGfUQc%3DA%40mail.gmail.com.