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Title: How decoherence affects the probability of slow-roll eternal inflation

Abstract

We present that 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. Finally, for a given potential, the delayedmore » decoherence can lead to slight quantitative adjustments to the regime in which the inflaton undergoes eternal inflation.« less

Authors:
 [1];  [2];  [2]
  1. Univ. of Hawaii, Honolulu, HI (United States). Department of Physics and Astronomy
  2. California Inst. of Technology (CalTech), Pasadena, CA (United States). Walter Burke Institute for Theoretical Physics
Publication Date:
Research Org.:
Univ. of Hawaii, Honolulu, HI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1424918
Alternate Identifier(s):
OSTI ID: 1373320
Grant/Contract Number:  
SC0010504; SC0011632
Resource Type:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 96; Journal Issue: 2; Journal ID: ISSN 2470-0010
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; Evolution of the universe; Inflation; open quantum systems and decoherence; quantum fields in curved spacetime; quantum gravity

Citation Formats

Boddy, Kimberly K., Carroll, Sean M., and Pollack, Jason. How decoherence affects the probability of slow-roll eternal inflation. United States: N. p., 2017. Web. doi:10.1103/PhysRevD.96.023539.
Boddy, Kimberly K., Carroll, Sean M., & Pollack, Jason. How decoherence affects the probability of slow-roll eternal inflation. United States. doi:10.1103/PhysRevD.96.023539.
Boddy, Kimberly K., Carroll, Sean M., and Pollack, Jason. Fri . "How decoherence affects the probability of slow-roll eternal inflation". United States. doi:10.1103/PhysRevD.96.023539. https://www.osti.gov/servlets/purl/1424918.
@article{osti_1424918,
title = {How decoherence affects the probability of slow-roll eternal inflation},
author = {Boddy, Kimberly K. and Carroll, Sean M. and Pollack, Jason},
abstractNote = {We present that 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. Finally, for a given potential, the delayed decoherence can lead to slight quantitative adjustments to the regime in which the inflaton undergoes eternal inflation.},
doi = {10.1103/PhysRevD.96.023539},
journal = {Physical Review D},
number = 2,
volume = 96,
place = {United States},
year = {2017},
month = {7}
}

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