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I understand that this is a much debated issue, so I will try to be precise in order to narrow the question. Bell inequality violation rules out Local Realism. From this, I understand that by giving up just one of the two conditions (Locality or Realism) one could generate a viable model. My questions:

  1. Could we provide a local and non realistic model that reproduces the observed correlations? (in particular I do not see how a local theory can reproduce correlations outside of the light cone)
  2. Could we provide a non local and realistic model that reproduces the observed correlations?
  3. What about QM? I this (non) local and/or (non) realistic? Is this just a matter of interpretation?

Claims on these points in the literature are often unclear and (to me) confusing (see for example http://www.physics.drexel.edu/~bob/Entanglement/aspect_nature446.pdf) so I would like to see explicit model for my points 1. and 2.

Arnaldo Maccarone
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2 Answers2

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There are a number of local theories that violate Bell's inequality. This is partially because there are lots of hidden assumptions in Bell's theory which are well described by Wiseman.

The best example I know of is a Event-based simulation of quantum physics experiments where they show that a simple classical event-based simulation can reproduce Bell-CHSH inequalities. It can also be done with negative probabilities. Neither of these are a complete theory, however.

Urb
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akvadrako
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1.) You have to give up not only Einstein-locality (locality itself would be unproblematic), but also causality, because there are variants of the proof which rely on causality only, with Reichenbach's principle of common cause as the base. I do not think theories which reject causality and realism make sense for a scientist, who wants to study the real world and find causal explanations for unexplained correlations. But, in principle, one could use the minimal interpretation of QT for this.

2.)+3.) There are realistic interpretations of QT, namely the de Broglie-Bohm interpretation.

Schmelzer
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