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How decoherence affects the probability of slow-roll eternal inflation

Boddy, Kimberly K. and Carroll, Sean M. and Pollack, Jason (2017) How decoherence affects the probability of slow-roll eternal inflation. Physical Review D, 96 (2). Art. No. 023539. ISSN 2470-0010. doi:10.1103/PhysRevD.96.023539.

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Slow-roll inflation can become eternal if the quantum variance of the inflaton field around its slowly rolling classical trajectory is converted into a distribution of classical spacetimes inflating at different rates, and if the variance is large enough compared to the rate of classical rolling that the probability of an increased rate of expansion is sufficiently high. Both of these criteria depend sensitively on whether and how perturbation modes of the inflaton interact and decohere. Decoherence is inevitable as a result of gravitationally sourced interactions whose strength are proportional to the slow-roll parameters. However, the weakness of these interactions means that decoherence is typically delayed until several Hubble times after modes grow beyond the Hubble scale. We present perturbative evidence that decoherence of long-wavelength inflaton modes indeed leads to an ensemble of classical spacetimes with differing cosmological evolutions. We introduce the notion of per-branch observables—expectation values with respect to the different decohered branches of the wave function—and show that the evolution of modes on individual branches varies from branch to branch. Thus, single-field slow-roll inflation fulfills the quantum-mechanical criteria required for the validity of the standard picture of eternal inflation. For a given potential, the delayed decoherence can lead to slight quantitative adjustments to the regime in which the inflaton undergoes eternal inflation.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Boddy, Kimberly K.0000-0003-1928-4667
Carroll, Sean M.0000-0002-4226-5758
Pollack, Jason0000-0003-4754-4905
Additional Information:© 2017 American Physical Society. Received 27 January 2017; published 28 July 2017. We thank the anonymous reviewer of the first draft of our manuscript for pointing out an error in our interpretation of Eq. (2) which affected our numerical results. K. B. is funded in part by U.S. Department of Energy (DOE) Grant No. DE-SC0010504. S. C. and J. P. are funded in part by the Walter Burke Institute for Theoretical Physics at Caltech, by DOE Grant No. DE-SC0011632, by the Foundational Questions Institute, and by the Gordon and Betty Moore Foundation through Grant No. 776 to the Caltech Moore Center for Theoretical Cosmology and Physics.
Group:Walter Burke Institute for Theoretical Physics, Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0010504
Walter Burke Institute for Theoretical Physics, CaltechUNSPECIFIED
Department of Energy (DOE)DE-SC0011632
Foundational Questions Institute (FQXI)UNSPECIFIED
Gordon and Betty Moore Foundation776
Caltech Moore Center for Theoretical Cosmology and PhysicsUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20170728-110444626
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79540
Deposited By: Tony Diaz
Deposited On:28 Jul 2017 23:29
Last Modified:15 Nov 2021 17:48

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