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Quantum Mechanics in the Light of Quantum Cosmology

Gell-Mann, Murray and Hartle, James B. (2018) Quantum Mechanics in the Light of Quantum Cosmology. . (Unpublished)

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We sketch a quantum mechanical framework for the universe as a whole. Within that framework we propose a program for describing the ultimate origin in quantum cosmology of the quasiclassical domain of familiar experience and for characterizing the process of measurement. Predictions in quantum mechanics are made from probabilities for sets of alternative histories. Probabilities can be assigned only to sets of histories that approximately decohere. Decoherence is defined and the mechanism of decoherence is reviewed. Decoherence requires a sufficiently coarse-grained description of alternative histories of the universe. A quasiclassical domain consists of a branching set of alternative decohering histories, described by a coarse graining that is maximally refined consistent with decoherence, with individual branches that exhibit a high level of classical correlation in time. A quasiclassical domain is emergent in the universe as a consequence of the initial condition and the action function of the elementary particles. It is an important question whether all the quasiclassical domains are roughly equivalent or whether there are various essentially inequivalent ones. A measurement is a correlation with variables in a quasiclassical domain. An observer (or information gathering and utilizing system) is a complex adaptive system that has evolved to exploit the relative predictability of a quasiclassical domain. We suggest that resolution of many of the problems of interpretation presented by quantum mechanics is to be accomplished, not by further scrutiny of the subject as it applies to reproducible laboratory situations, but rather by an examination of alternative histories of the universe, stemming from its initial condition, and a study of the problem of quasiclassical domains.

Item Type:Report or Paper (Discussion Paper)
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Additional Information:This paper was the first in a series by the two authors developing a quantum mechanical framework for the universe as a whole called Decoherent Histories Quantum Mechanics, DH. Although developed independently, and differing on certain points, DH has much in common with with Robert Griffiths' and Roland Omnès' earlier consistent histories formulation of quantum mechanics as explicitly acknowledged. The paper has not been updated or improved and the references are unchanged. The paper appeared in the Proceedings of the Santa Fe Institute Workshop on Complexity, Entropy, and the Physics of Information, May 1989 and in the Proceedings of the 3rd International Symposium on The Foundations of Quantum Mechanics in the Light of New Technology, Tokyo, Japan, August 1989. It is posted here to make it accessible to those who might not have easy access to the published sources. One of us, MG-M, would like to acknowledge the great value of conversations about the meaning of quantum mechanics with Felix Villars and Richard Feynman in 1963-64 and again with Richard Feynman in 1987-88. He is also very grateful to Valentine Telegdi for discussions during 1985-86, which persuaded him to take up the subject again after twenty years. Both of us are indebted to Telegdi for further interesting conversations since 1987. We would also like to thank R. Griffiths for a useful communication and a critical reading of the manuscript and R. Penrose for a helpful discussion. Part of this work was carried out at various times at the Institute for Theoretical Physics, Santa Barbara, the Aspen Center for Physics, the Santa Fe Institute, and the Department of Applied Mathematics and Theoretical Physics, University of Cambridge. We are grateful for the hospitality of these institutions. The work of JBH was supported in part by NSF grant PHY85-06686 and by a John Simon Guggenheim Fellowship. The work of MG-M was supported in part by the U.S. Department of Energy under contract DE-AC-03-81ER40050 and by the Alfred P. Sloan Foundation.
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John Simon Guggenheim FoundationUNSPECIFIED
Department of Energy (DOE)DE-AC-03-81ER40050
Alfred P. Sloan FoundationUNSPECIFIED
Record Number:CaltechAUTHORS:20190429-083802697
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95066
Deposited By: Tony Diaz
Deposited On:29 Apr 2019 15:48
Last Modified:29 Apr 2019 15:48

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