Jarek wrote:Indeed, while our intuition demands it, there are now no doubts that "local realism" is incorrect.

The question is how to repair it without referring to magic - like building models based on physical assumptions, which are also able to violate such inequalities - by the way pointing where our "local realism" intuition is wrong.

My point here is that this missing assumption is time/CPT symmetry, which is at heart of (Lagrangian mechanics) theories we use in all scales: from QFT, unitary QM to GRT, but is against our natural intuition: which is very time-asymmetric.

Using time-symmetric "4D local realism" instead: in space-time, the basic object is no longer particle, but its trajectory - continuous for 4D locality.

Ensembles of such objects: Feynman in QM, or statistical physics: Boltzmann in MERW, for example, have strong Anderson localization - like real physics, unlike standard diffusion - which is local in standard sense and often very wrong, while MERW is nonlocal in a standard sense ... but is local in the 4D sense: is just path ensemble.

And the constructions here show that we get also other nonintuitive quantum properties from "4D local realism": using path ensembles - Born rule and resulting Bell violation.

What do think about such "4D local realism: path ensembles" explanation of quantum "spookiness"? Do you know a better explanation?

I think there is a better explanation. It was discovered by Slava Belavkin (RIP) and called "eventum mechanics". It admits that time is asymmetric and it puts time and causality into the QM picture, getting a true synthesis of the Born law and the usual "unitary" QM. Born law is not an uncomfortable add-on, but an intrinsic part of the dynamics. Belavkin's programme was not followed up and he had an untimely death. However, we know that the framework is compatible with Lorentz invariance. It embodies irreducible randomness and, for want of a better word, spooky action at a distance. (But it could better be called more "passion" than "action"; it is not malevolent or scary, one could better call it "angelic").

https://arxiv.org/abs/0905.2723

Schrödinger's cat meets Occam's razor

Richard D. Gill

Unpublished, incomplete

(I'm looking for a co-author to help me finish it!)

We discuss V.P. Belavkin's approach to the measurement problem encapsulated in his theory of eventum mechanics (as presented in his 2007 survey). In particular, we show its relation to ideas based on superselection and interaction with the environment developed by N.P. Landsman (1995, and more recent papers).

Landsman writes "those believing that the classical world exists intrinsically and absolutely [such persons later termed by him B-realists] are advised against reading this [his, 1995] paper". He adopts a milder position, calling it that of an A-realist: we live in a classical world but to give it special status is like insisting that the Earth is the centre of the universe. The B-realists are accused of living under some kind of hallucination. Landsman presents arguments pointing in a particular direction to a resolution of the measurement problem which at least would satisfy the A-realists. We point out in this paper that the theory earlier developed by Belavkin (surveyed in his 2007 paper) seems to complete Landsman's program or at least exhibits a "realisation" satisfying his desiderata. At the same time it seems that this completion of the program ends up giving both A- and B-realists equal licence to accuse the others of living under hallucinations.

https://arxiv.org/abs/1207.5103

Statistics, Causality and Bell's Theorem

Richard D. Gill

Journal reference: Statistical Science 2014, Vol. 29, No. 4, 512-528

DOI: 10.1214/14-STS490

Bell's [Physics 1 (1964) 195-200] theorem is popularly supposed to establish the nonlocality of quantum physics. Violation of Bell's inequality in experiments such as that of Aspect, Dalibard and Roger [Phys. Rev. Lett. 49 (1982) 1804-1807] provides empirical proof of nonlocality in the real world. This paper reviews recent work on Bell's theorem, linking it to issues in causality as understood by statisticians. The paper starts with a proof of a strong, finite sample, version of Bell's inequality and thereby also of Bell's theorem, which states that quantum theory is incompatible with the conjunction of three formerly uncontroversial physical principles, here referred to as locality, realism and freedom. Locality is the principle that the direction of causality matches the direction of time, and that causal influences need time to propagate spatially. Realism and freedom are directly connected to statistical thinking on causality: they relate to counterfactual reasoning, and to randomisation, respectively. Experimental loopholes in state-of-the-art Bell type experiments are related to statistical issues of post-selection in observational studies, and the missing at random assumption. They can be avoided by properly matching the statistical analysis to the actual experimental design, instead of by making untestable assumptions of independence between observed and unobserved variables. Methodological and statistical issues in the design of quantum Randi challenges (QRC) are discussed. The paper argues that Bell's theorem (and its experimental confirmation) should lead us to relinquish not locality, but realism.