Unimodular Hartle-Hawking wave packets and their probability interpretation
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Published version
Author(s)
Alexandre, Bruno
Magueijo, Joao
Type
Journal Article
Abstract
We reexamine the Hartle-Hawking wave function from the point of view of a quantum theory which
starts from the connection representation and allows for off-shell nonconstancy of Λ (as in unimodular
theory), with a concomitant dual relational time variable. By translating its structures to the metric
representation we find a nontrivial inner product rendering wave packets of Hartle-Hawking waves
normalizable and the time evolution unitary; however, the implied probability measure differs
significantly from the naive jψj
2. In contrast with the (monochromatic) Hartle-Hawking wave function,
these packets form traveling waves with a probability peak describing de Sitter space, except near the
bounce, where the incident and reflected waves interfere, transiently recreating the usual standing wave.
Away from the bounce the packets get sharper both in metric and connection space, an apparent
contradiction with Heisenberg’s principle allowed by the fact that the metric is not Hermitian, even
though its eigenvalues are real. Near the bounce, the evanescent wave not only penetrates into the
classically forbidden region but also extends into the a2 < 0 Euclidean domain. We work out the
propagators for this theory and relate them to the standard ones. The a ¼ 0 point (aka the “nothing”) is
unremarkable, and in any case a wave function peaked therein is typically non-normalizable and/or
implies a nonsensical probability for Λ (which the Universe would preserve forever). Within this theory it
makes more sense to adopt a Gaussian state in an appropriate function of Λ, and use the probability
associated with the evanescent wave present near the time of the bounce as a measure of the likelihood of
creation of a pair of time-symmetric semiclassical Universes.
starts from the connection representation and allows for off-shell nonconstancy of Λ (as in unimodular
theory), with a concomitant dual relational time variable. By translating its structures to the metric
representation we find a nontrivial inner product rendering wave packets of Hartle-Hawking waves
normalizable and the time evolution unitary; however, the implied probability measure differs
significantly from the naive jψj
2. In contrast with the (monochromatic) Hartle-Hawking wave function,
these packets form traveling waves with a probability peak describing de Sitter space, except near the
bounce, where the incident and reflected waves interfere, transiently recreating the usual standing wave.
Away from the bounce the packets get sharper both in metric and connection space, an apparent
contradiction with Heisenberg’s principle allowed by the fact that the metric is not Hermitian, even
though its eigenvalues are real. Near the bounce, the evanescent wave not only penetrates into the
classically forbidden region but also extends into the a2 < 0 Euclidean domain. We work out the
propagators for this theory and relate them to the standard ones. The a ¼ 0 point (aka the “nothing”) is
unremarkable, and in any case a wave function peaked therein is typically non-normalizable and/or
implies a nonsensical probability for Λ (which the Universe would preserve forever). Within this theory it
makes more sense to adopt a Gaussian state in an appropriate function of Λ, and use the probability
associated with the evanescent wave present near the time of the bounce as a measure of the likelihood of
creation of a pair of time-symmetric semiclassical Universes.
Date Issued
2023-03-15
Date Acceptance
2023-02-14
Citation
Physical Review D, 2023, 107 (6)
ISSN
2470-0010
Publisher
American Physical Society
Journal / Book Title
Physical Review D
Volume
107
Issue
6
Copyright Statement
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
License URL
Identifier
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Subjects
Astronomy & Astrophysics
Physical Sciences
Physics
Physics, Particles & Fields
QUANTUM COSMOLOGY
RELATIVITY
Science & Technology
TIME
Publication Status
Published
Article Number
ARTN 063501
Date Publish Online
2023-03-01