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Published April 15, 1994 | public
Journal Article Open

Path integrals, density matrices, and information flow with closed timelike curves


Two formulations of quantum mechanics, inequivalent in the presence of closed timelike curves, are studied in the context of a soluable system. It illustrates how quantum field nonlinearities lead to a breakdown of unitarity, causality, and superposition using a path integral. Deutsch's density matrix approach is causal but typically destroys coherence. For each of these formulations I demonstrate that there are yet further alternatives in prescribing the handling of information flow (inequivalent to previous analyses) that have implications for any system in which unitarity or coherence is not preserved.

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©1994 The American Physical Society. Received 2 September 1993. The author wishes to thank J. Preskill for his continuing interest, patient explications, probing questions, and constructive criticism. This work was supported in part by the U. S. Department of Energy under Grant No. DE-FG03-92-ER40701.


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August 22, 2023
August 22, 2023