On 6/06/2016 7:41 am, Brent Meeker wrote:
On 6/5/2016 4:01 AM, Bruno Marchal wrote:
On 05 Jun 2016, at 01:26, Bruce Kellett wrote:
Locally, Alice and Bob can simulate anything they like, and they can
simulate universes with non-local hidden variables, and predict
that within those worlds the Bell inequalities are violated. But
when they get back to their own world and compare their results,
they will find that the correlations between their separate
simulations of the results of spin measurements at arbitrary angles
invariably satisfy the inequalities. In other words, they cannot,
jointly, simulate the quantum results in any world that they both
inhabit. The MWI view from outside is no different -- non-locality
is inescapable.
You don't need to simulate hidden non- local variable. You need to
just simulate the wave function.
Which depends on both spatial variables of the particles in an EPR
experiment and so it non-local.
Precisely. I think there is some degree of confusion around the terms
'local' and 'non-local'. The wave function is non-local in that it
refers to the two separated particles as a single entity, without
specifying any particular interaction between them. This is a simple
consequence of the fact that the wave function resides in configuration
space, and any suggestion of a 'local mechanical' connection between the
remote particles is lost when we move back into physical space in order
to compare the quantum predictions coming from the wave function to our
experimental results.
When people ask for a 'local' explanation of anything, they are thinking
in terms of a 'mechanism', such as the exchange of particle that can
carry information in a local way. If they think of a 'non-local'
interaction, they still think in this mechanistic way by considering a
faster-than-light tachyonic exchange that is completely analagous to the
subluminal particle exchange characteristic of normal local
interactions. Such thinking is inapplicable to the wave function in
quantum mechanics. When the wave function is describing two or more
particles, it is intrinsically non-local in that in certain
circumstances the wave function describes a single state, even though
its parts might be widely separated in space. This form of intrinsic
non-locality does not have any 'mechanism' underlying it -- there is no
subluminal or superluminal particle exchange going on in the background
to hold the dispersed state together! The non-locality is intrinsic: it
cannot be reduced to some local mechanistic account.
Bruce
Brent
It will take a super-exponential time to do so, but the many couples
of Alice and Bob will all (except for a negligeable subset) detect
non-locality in their respective branches, although we, from outside,
will know that noting non-local ever happened. The non-locality will
only be a FPI statistical appearances.
It is the same for "our" multiverse. It obeys a deterministic local
equations, and non-locality in all branches are a local relative
appearance, like the indeterminacy itself.
Bruno
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