On Thu, Oct 3, 2019 at 7:08 PM Bruno Marchal <[email protected]> wrote:
> > On 1 Oct 2019, at 19:37, 'Brent Meeker' via Everything List < > [email protected]> 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 [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLSewE7FaznrJTY6OeQO240hqKX4DSm6rW1743PGfUQc%3DA%40mail.gmail.com.
