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arXiv:1203.1504

Does Geometric Algebra provide a loophole to Bell's Theorem? (with corrections)

Richard David Gill

Published Mar 7, 2012• 10 citations

Abstract

In 2007, and in a series of later papers, Joy Christian claimed to refute Bell's theorem, presenting an alleged local realistic model of the singlet correlations using techniques from Geometric Algebra (GA). Several authors published papers refuting his claims, and Christian's ideas did not gain acceptance. However, he recently succeeded in publishing yet more ambitious and complex versions of his theory in fairly mainstream journals. How could this be? The mathematics and logic of Bell's theorem is simple and transparent and has been intensely studied and debated for over 50 years. Christian claims to have a mathematical counterexample to a purely mathematical theorem. Each new version of Christian's model used new devices to circumvent Bell's theorem or depended on a new way to misunderstand Bell's work. These devices and misinterpretations are in common use by other Bell critics, so it useful to identify and name them. I hope that this paper can serve as a useful resource to those who need to evaluate new "disproofs of Bell's theorem". Christian's fundamental idea is simple and quite original: he gives a probabilistic interpretation of the fundamental GA equation a.b = (ab + ba)/2. After that, ambiguous notation and technical complexity allow sign errors to be hidden from sight, and new mathematical errors can be introduced.

DOI: 10.3390/e22010061

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I point out a simple algebraic error in Joy Christian’s refutation of Bell’s theorem. In substituting the result of multiplying some derived bivectors with one another by consultation of their multiplication table, he confuses the generic vectors which he used to define the table, with other specific vectors having a special role in the paper, which had been introduced earlier. The result should be expressed in terms of the derived bivectors which indeed do follow this multiplication table. When correcting this calculation, the result is not the singlet correlation any more. Moreover, curi-ously, his normalized correlations are independent of the number of measurements and certainly do not require letting n converge to infinity. At the same time, his unnormalized or raw correlations are identically equal to −1, independently of the number of measurements! Correctly computed, his standardized correlations are the bivectors −a · b − a ∧ b, and they find their origin entirely in his normalization or standardization factors. I conclude that his research program has been set up around an elaborately hidden but trivial mistake.

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Comments on "Disproof of Bell's theorem"

Florin Moldoveanu

In a series of very interesting papers [1-7], Joy Christian constructed a counterexample to Bell's theorem. This counterexample does not have the same assumptions as the original Bell's theorem, and therefore it does not represent a genuine disproof in a strict mathematical sense. However, assuming the physical relevance of the new assumptions, the counterexample is shown to be a contextual hidden variable theory. If Bell's theorem's importance is to rule out contextual hidden variable theories obeying relativistic locality, then Joy Christian's counterexample achieves its aim. If however contextual hidden variables theories are not considered genuine physically theories and Bell's theorem's importance stems from its ability to be experimentally confirmed, then Joy Christian's counterexample does not diminish the importance of Bell's theorem. The implications of Joy Christian's counterexample are discussed in the context of information theory. Version 2 note: Subsequent analysis disproved the mathematical consistency of Joy Christian's model. This paper was based on the assumption of the mathematical validity of the model. Except for the addition of this note, the content of this paper was not modified in any other way.

arXiv:1107.1007•Jul 6, 2011•1 citation

The Scope and Generality of Bell's Theorem

James Owen Weatherall

I present a local, deterministic model of the EPR-Bohm experiment, inspired by recent work by Joy Christian, that appears at first blush to be in tension with Bell-type theorems. I argue that the model ultimately fails to do what a hidden variable theory needs to do, but that it is interesting nonetheless because the way it fails helps clarify the scope and generality of Bell-type theorems. I formulate and prove a minor proposition that makes explicit how Bell-type theorems rule out models of the sort I describe here.

•Jan 1, 2012•3 citations

In 2007, and in a series of later papers, Joy Christian claimed to refute Bell's theorem, presenting an alleged local realistic model of the singlet correlations using techniques from Geometric Algebra (GA). Several authors published papers refuting his claims, and Christian's ideas did not gain acceptance. However, he recently succeeded in publishing yet more ambitious and complex versions of his theory in fairly mainstream journals. How could this be? The mathematics and logic of Bell's theorem is simple and transparent and has been intensely studied and debated for over 50 years. Christian claims to have a mathematical counterexample to a purely mathematical theorem. Each new version of Christian's model used new devices to circumvent Bell's theorem or depended on a new way to misunderstand Bell's work. These devices and misinterpretations are in common use by other Bell critics, so it useful to identify and name them. I hope that this paper can serve as a useful resource to those who need to evaluate new "disproofs of Bell's theorem". Christian's fundamental idea is simple and quite original: he gives a probabilistic interpretation of the fundamental GA equation a.b = (ab + ba)/2. After that, ambiguous notation and technical complexity allow sign errors to be hidden from sight, and new mathematical errors can be introduced.

Four critical elementary mathematical mistakes in Joy Christian's counterexample to Bell's theorem are presented. Consequently, Joy Christian's hidden variable model cannot reproduce any quantum mechanics results and cannot be used as a counterexample to Bell's theorem. The mathematical investigation is followed by a short discussion about the possibility to construct other hidden variable theories. A tutorial section on relevant Clifford algebra topics was added at the end to help interested readers decide for themselves the validity of Joy's claims. Also an appendix section discusses recent developments.

I point out a simple algebraic error in Joy Christian’s refutation of Bell’s theorem. In substituting the result of multiplying some derived bivectors with one another by consultation of their multiplication table, he confuses the generic vectors which he used to define the table, with other specific vectors having a special role in the paper, which had been introduced earlier. The result should be expressed in terms of the derived bivectors which indeed do follow this multiplication table. When correcting this calculation, the result is not the singlet correlation any more. Moreover, curi-ously, his normalized correlations are independent of the number of measurements and certainly do not require letting n converge to infinity. At the same time, his unnormalized or raw correlations are identically equal to −1, independently of the number of measurements! Correctly computed, his standardized correlations are the bivectors −a · b − a ∧ b, and they find their origin entirely in his normalization or standardization factors. I conclude that his research program has been set up around an elaborately hidden but trivial mistake.

In a series of very interesting papers [1-7], Joy Christian constructed a counterexample to Bell's theorem. This counterexample does not have the same assumptions as the original Bell's theorem, and therefore it does not represent a genuine disproof in a strict mathematical sense. However, assuming the physical relevance of the new assumptions, the counterexample is shown to be a contextual hidden variable theory. If Bell's theorem's importance is to rule out contextual hidden variable theories obeying relativistic locality, then Joy Christian's counterexample achieves its aim. If however contextual hidden variables theories are not considered genuine physically theories and Bell's theorem's importance stems from its ability to be experimentally confirmed, then Joy Christian's counterexample does not diminish the importance of Bell's theorem. The implications of Joy Christian's counterexample are discussed in the context of information theory. Version 2 note: Subsequent analysis disproved the mathematical consistency of Joy Christian's model. This paper was based on the assumption of the mathematical validity of the model. Except for the addition of this note, the content of this paper was not modified in any other way.

I present a local, deterministic model of the EPR-Bohm experiment, inspired by recent work by Joy Christian, that appears at first blush to be in tension with Bell-type theorems. I argue that the model ultimately fails to do what a hidden variable theory needs to do, but that it is interesting nonetheless because the way it fails helps clarify the scope and generality of Bell-type theorems. I formulate and prove a minor proposition that makes explicit how Bell-type theorems rule out models of the sort I describe here.