On 5/06/2016 3:31 am, Bruno Marchal wrote:
On 04 Jun 2016, at 01:28, Bruce Kellett wrote:
Sure, Bell's theorem only rules out local hidden variables. If you
simulate non-local hidden variables (i.e., get the separated
experimenters to communicate non-locally), then of course you can
reproduce the quantum correlations. But I was under the impression
that the computationalist goal was to eliminate non-locality.
Separated experimenters, with as much computing power as necessary,
cannot simulate the quantum correlations by performing only local
computations.
You can simulate the whole (multiversial) structure, and the observers
will find that from their perspective, Bell's inequality are violated.
From outside, we can see (like Everett saw) that it is just a case of
self-duplication FPI. (Which brings us back to the preceding thread of
course).
I think you are trying to move the goal posts here.... The original
argument about non-locality in MWI was the contention by people like
Price, Tipler, Brown, and Christian that Bell made certain assumptions
that were not true in the Everetttian approach. Their conclusion was
that his theorem was not applicable to the MWI, rendering the argument
that local hidden variables were ruled out inapplicable in that case.
(Though Joy Christian tries to go further and argues that Bell made a
trivial mistake that rendered his 'theorem' invalid in all
interpretations.) I have rebutted the various claims of these papers in
other posts: Bell does not depend on such ill-defined things as
counterfactual definiteness, and certainly does not assume that
experiments have only single outcomes. My conclusion is that Bell's
theorem is valid universally -- merely changing the interpretation does
not alter that, and thus non-locality has been shown to be intrinsic to
quantum mechanics.
You are now attempting to change the argument: you appear now to accept
that individual experimenters will see the quantum world as non-local,
but that this is merely an observer-dependent effect, arising from
self-location in the multiverse: another instance of FPI. I think that
you have to do a bit more work on this changed approach to non-locality:
I think you will find that the argument does not work like the FPI
account of apparent indeterminism in a deterministic universe. Bell's
theorem applies to every set of correlations obtained by experimenters
in every branch of the universal wave function -- there is no 'external'
perspective from which Bell' s theorem does not apply. If there were,
there would have to be a local account available from the 'bird'
perspective, and there is no such account. If you claim that there is,
then the onus is on you to produce that account. The singlet state
|psi> = (|+>|-> - |->|+>)/sqrt(2)
is the wave function from the 'bird' perspective, and particles 1 and 2
are separated in the 'bird' perspective as much as in any 'frog'
perspective. Going outside the perspective of the individual
experimenters does not actually gain you anything in this instance.
Bruce
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