Boltzmann brains and the scale-factor cutoff measure of the multiverse
Name
De Simone-2010-Boltzmann brains and.pdf
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Author(s)
De Simone, Andrea
Guth, Alan
Linde, Andrei
Noorbala, Mahdiyar
Salem, Michael P.
Vilenkin, Alexander
Date Issued
September 2010
Journal
Physical Review D
Publisher
American Physical Society
Citation
De Simone, Andrea. et al. "Boltzmann brains and the scale-factor cutoff measure of the multiverse." Physical Review D 82.6 (2010): 063520. © 2010 The American Physical Society
Version
Final published version
Abstract
To make predictions for an eternally inflating “multiverse,” one must adopt a procedure for regulating its divergent spacetime volume. Recently, a new test of such spacetime measures has emerged: normal observers—who evolve in pocket universes cooling from hot big bang conditions—must not be vastly outnumbered by “Boltzmann brains”—freak observers that pop in and out of existence as a result of rare quantum fluctuations. If the Boltzmann brains prevail, then a randomly chosen observer would be overwhelmingly likely to be surrounded by an empty world, where all but vacuum energy has redshifted away, rather than the rich structure that we observe. Using the scale-factor cutoff measure, we calculate the ratio of Boltzmann brains to normal observers. We find the ratio to be finite, and give an expression for it in terms of Boltzmann brain nucleation rates and vacuum decay rates. We discuss the conditions that these rates must obey for the ratio to be acceptable, and we discuss estimates of the rates under a variety of assumptions.
MIT Department
Massachusetts Institute of Technology. Center for Theoretical Physics
Massachusetts Institute of Technology. Department of Physics
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1103/PhysRevD.82.063520
