On 05 Jun 2016, at 08:39, Bruce Kellett wrote:
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,
He is forced to use it when he talk about some Alice and Bob doing a
simultaneous measurement and getting definite outcome.
and certainly does not assume that experiments have only single
outcomes.
Then he show non-locality appearance in all branch, but it does not
show the need of any non-local action for that. he proves just the
many-world.
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.
Then he shows only appearance of non-locality on (almost) all
branches, or entangled relative states. Only when we abstract all
branches and keep one, does action at a distance needed to violate the
inequality.
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:
That is what I try to explain since the beginning. Indeterminacy and
non-locality are statistical first person plural appearances.
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,
But that exists: the Schroedinger wave equation.
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.
But it makes no sense to say that particles 1 and 2, when separated,
belongs to the same branches. Bell can say that because it assumes
only one branch (so to speak) in which case there is a mysterious
spooky action at a distance. But if they are space-like separated, we
get the non-locality appearances only for those Alice and Bob wich
will be able to meet at some points, and the math shows that this
linearly and locally implied such appearances, despite the wave
evolved locally at all time in the phase space. There should be no
problem as you seem to accept the definition of worlds by set of
events/objects close for interaction. If Alice and Bob are space like
separated, they just cannot belong to the same woirld: it makes no
sense.
Bruno
Bruce
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