A Proposed Test of the Local Causality of Spacetime
- 987 Downloads
A theory governing the metric and matter fields in spacetime is locally causal if the probability distribution for the fields in any region is determined solely by physical data in the region's past, i.e. it is independent of events at space-like separated points. General relativity is manifestly locally causal, since the fields in a region are completely determined by physical data in its past. It is natural to ask whether other possible theories in which the fundamental description of space-time is classical and geometric—for instance, hypothetical theories which stochastically couple a classical spacetime geometry to a quantum field theory of matter—might also be locally causal.
A quantum theory of gravity, on the other hand, should allow the creation of spacetimes which violate local causality at the macroscopic level. This paper describes an experiment to test the local causality of spacetime, and hence to test whether or not gravity behaves as quantum theories of gravity suggest, in this respect. The experiment will either produce direct evidence that the gravitational field is not locally causal, and thus weak confirmation of quantum gravity, or else identify a definite limit to the domain of validity of quantum theory.
KeywordsQuantum Theory Local Causality Measurement Choice CHSH Inequality Bell Experiment
Unable to display preview. Download preview PDF.
- 1.C. Møller, in Les Theories Relativistes de la Gravitation, A. Lichnerowicz and M. Tonnelat (eds.) (CNRS, Paris, 1962).Google Scholar
- 3.T. Kibble, in Quantum Gravity 2: A Second Oxford Symposium, C. Isham, R. Penrose and D. Sciama (eds.) (Oxford University Press, Oxford, 1981).Google Scholar
- 6.R. Penrose, The Emperor's New Mind (Oxford University Press, Oxford, 1999) and refs therein.Google Scholar
- 9.J.S. Bell, “The Theory of Local Beables,” Epistemological Letters, 9, March 1976; reprinted in Dialectica 39 85–96 (1985) and in ; J.S. Bell, “Free Variables and Local Causality,” Epistemological Letters, 15, February 1977; reprinted in Dialectica 39 103–106 (1985) and in .Google Scholar
- 11.J. Henson, “Comparing Causality Principles,” quant-ph/0410051.Google Scholar
- 12.F. Dowker, private communication (2005).Google Scholar
- 16.J.S. Bell, Speakable and Unspeakable in Quantum Mechanics (Cambridge University Press, 1987).Google Scholar