Talk:Bell's theorem

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What is called correlations[edit]

To Jochen Burghardt and Arthur Rubin: isn't it better to first discuss the matter here rather than edit forth and back? Boris Tsirelson (talk) 07:19, 7 January 2015 (UTC)

Probably you're right - I didn't expect the issue to be that much complicated. Also, I can't help much in answering questions, as I'm not a physicist, but just a mathematician who wants to understand the article. Arthur Rubin is right in that the caption of File:Bell's theorem.svg explicitly mentions "spin-half". On the other hand, section Bell's_theorem#CHSH inequality speaks about "binary (+/-1 valued) outcomes". Maybe, the "outcome" is a normalized (i.e. scaled by 2 in our case) version of the measured "spin"? As another suggestion, the easiest way to obtain consistency might be to stick with the statistical notion of correlation, unless this is absolutely unusual in quantum physics. - Jochen Burghardt (talk) 18:15, 7 January 2015 (UTC)
I do not think it is complicated (and I am a kind of expert in it). Artur Rubin is right if the spin is treated as mechanical (the angular momentum); in this sense it is really neither 1 nor 1/2 but (plus-minus) a half of the Planck constant. But! This mechanics is rather irrelevant. Here the spin is treated informationally, as just a yes-no observable, encoded (for convenience) as plus-minus 1. (And by the way, the Stern–Gerlach experiment gives just this: splits the electron beam in two beams, without indicating "plus-minus how much" is it, really.)
About the statistical notion of correlation: the quantum calculation in the singlet state shows that the average spins (the expectations) are zero, and therefore there is no conflict between the two "correlations". However, when discussing Bell inequalities, it is usual indeed to call "correlations" the expected product in every case, whether or not the expectations are zero. Boris Tsirelson (talk) 19:14, 7 January 2015 (UTC)

Psychological Aspects[edit]

This article makes no mention of the psychology of the observers. Such factors as memory, subjectivity, and interpretation influence the results that each observer perceives and what they can agree on. Even without a many-worlds interpretation, each observer only perceives part of the entire reality. Which part they perceive affects the correlation. — Preceding unsigned comment added by 153.203.90.130 (talk) 20:05, 23 March 2015 (UTC)