On 12-05-2016 08:14, Bruce Kellett wrote:
The proof of non-locality, even in a many worlds model, is immediate. Since the sequence under consideration comes from a series of quantum events it must violate the Bell inequalities. And Bell has shown that these inequalities must hold for any local theory. Hence quantum mechanics, even in the many worlds interpretation, is non-local.
Bell showed that any local hidden variable explanation that would do away with the randomness in quantum mechanics is ruled out. This has no bearing on the MWI, or just plain QM, as the randomness remains.
In the MWI the branches that effectively appear due to decoherence do not contain well defined hidden variables. Suppose e.g. that I measure the z-component if a spin that was initially polarized in the y-direction. The two branches where I find the two different outcomes can be evolved back in time, so you can write some state before I did the measurement as a superposition of these two states. But these states are not effective branches where I would get localized in before the measurement.
So, Bells's theorem rules out that you can use inverse time evolution, and project out the definite future outcomes and construct a local hidden variable theory this way.
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