On 9/05/2016 1:39 am, Bruno Marchal wrote:
Thanks Scerir. Very interesting.
On 08 May 2016, at 09:58, 'scerir' via Everything List wrote:
https://arxiv.org/abs/1501.03521
'Bell on Bell's theorem: The changing face of nonlocality'
Authors: Harvey R. Brown, Christopher G. Timpson
there are several interesting points here
ch. 9 - Locality in the Everett picture
ch. 9.1 EPR and Bell correlations in the Everettian setting
Nice.
I think that what we are trying to explain to Bruce is well summed up
in their section 9.1.2 (the Everett description of the singlet state,
case of non-align polarizer).
I have already discussed this in my reply to Saibal. The basic point I
would make again is that the splitting of the universal wave function
into separate "worlds" is an interpretive gloss that does not actually
alter anything in the theory. Furthermore, 'who knows what about
whatever' is also an irrelevance as far as the universal wave function
is concerned. If you are going to work in the many worlds paradigm, then
everything ultimately stems from the unitary evolution of the universal
wave function -- all else is just interpretive gloss, of no fundamental
significance.
This is the case for the discussion in section 9.1.2 of the paper by
Brown and Timpson. Their equation (9) contains all the relevant results
that set the universal wave function -- the additional third measurement
(or measurement-like interaction) leading to equation (10) is,
therefore, irrelevant. All that happens in eq. (10) is an exchange of
information -- but it is an exchange of information that is already
present in the universal wave function, no new information is created at
this point. Just like opening the box on Schrödinger's cat, which is
either alive or dead long before, looking changes nothing. Eq. (10) is,
similarly, just an interpretive gloss of no fundamental significance.
The important point here is that everything is set in the universal wave
function /before/ Alice and Bob meet. The relative angle of the
respective polarizers is set in the wave function long before the light
cones of Alice and Bob overlap, so that relative angle is determined
non-locally.
The universal wave function is not a local object -- the unitary
evolution does not have any implicit notion of locality. Locality is a
human convention, and the universal wave function is under no compulsion
to take any notice of human conventions or preferences.
Bruce
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