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SUMMARY:Causality\, Bell's Theorem and Ontic Definiteness - Joe Henson (Pe
 rimeter Institute)
DTSTART:20101118T141500Z
DTEND:20101118T151500Z
UID:TALK27636@talks.cam.ac.uk
CONTACT:Ashley Montanaro
DESCRIPTION:Bell's theorem shows that the reasonable relativistic causal p
 rinciple known as "local causality" is not compatible with the predictions
  of quantum mechanics.  As will be argued in the talk\, it is impossible t
 o maintain a satisfying causal principle of this type while dropping any o
 f the better-known assumptions of Bell's theorem. However\, another (seldo
 m challenged) assumption of Bell's theorem is the use of classical logic. 
 One part of this assumption is the principle of ontic definiteness\, that 
 is\, that it must in principle be possible to assign definite truth values
  to all propositions treated in the theory.\n\nIn this talk it will be sho
 wn that\, once the logical setting is clarified somewhat\, rejecting this 
 principle does not in any way undermine the type of causal principle used 
 by Bell. Without ontic definiteness\, the deterministic causal condition k
 nown as Einstein Locality succeeds in banning superluminal influence (incl
 uding signalling) whilst allowing correlations that violate Bell's inequal
 ities. Objections to altering logic\, and the consequences for operational
  and realistic viewpoints\, will be discussed.\n
LOCATION:MR4\, Centre for Mathematical Sciences
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