Q+ Hangout: Howard Wiseman
Date/time: Wed. 26th Nov. 2014 10pm GMT/UTC
Speaker: Howard Wiseman (Griffith University)
Title: After 50 years, Bell's Theorem Still Reverberates
Fifty years ago this month, Belfast-born physicist John Bell submitted for publication a paper  which has been described as “the most profound discovery in science” . However, its significance is still much disputed by physicists and philosophers [3, 4]. I will explain what is so puzzling about the types of correlations Bell introduced, by a specific example based on . (For those well-versed in Bell inequalities this may still be of pedagogical interest.) But what exactly do these Bell-type correlations violate? Bell’s original answer  was the joint assumptions of determinism and locality. His later answer  was the single assumption of local causality (which, confusingly, he sometimes also called locality). Different ‘camps’ of physicists – operationalists and realists respectively – prefer the different versions of Bell’s theorem.
Which of Bell’s notions, locality or local causality, expresses the causal structure of Einstein’s theory of relativity? I will argue for the answer: neither [3,4]. Both notions require an additional causal assumption, and the one required for local causality is a stronger one. I will discuss how the different assumptions fit with the ideologies of the two camps, and how they can best be reconciled.
 J. S. Bell, “On the Einstein-Podolsky-Rosen paradox”, Physics 1, 195-200 (1964).
 H. P. Stapp, “Are superluminal connections necessary?”, Nuovo Cim. 40B, 191 (1977).
 H. M. Wiseman, “The two Bell’s theorems of John Bell”, J. Phys. A 47, 424001 (2014) (Invited Review for Special Issue, 50 years of Bell’s theorem)
 H. M. Wiseman, “Bell’s theorem still reverberates”, Nature 510, 467-9 (2014).
 P. K. Aravind, “Bell’s theorem without inequalities and only two distant observers”, Found. Phys. Lett. 15, 397 (2002).
 J. S. Bell, “The Theory of Local Beables”, Epistemological Lett. 9, 11-24 (1976).
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