Unitary and Vilenkin's wave functions
File(s)PhysRevD.108.023526.pdf (382.98 KB)
Published version
Author(s)
Alexandre, Bruno
Isichei, Raymond
Magueijo, Joao
Type
Journal Article
Abstract
It is remarkably difficult to reconcile unitarity and Vilenkin’s wave function. For example, the natural conserved inner product found in quantum unimodular gravity applies to the Hartle-Hawking wave function, but fails for its Vilenkin counterpart. We diagnose this failure from different angles (Laplace transform instead of Fourier transform, non-Hermiticity of the Hamiltonian, etc.) to conclude that ultimately it stems from allowing the connection to become imaginary in a section of its contour. In turn this is the unavoidable consequence of representing the Euclidean theory as an imaginary image within a fundamentally Lorentzian theory. It is nonetheless possible to change the underlying theory and replace the connection’s foray into the imaginary axis by an actual signature change (with the connection, action and Hamiltonian remaining real). The structural obstacles to unitarity are then removed, but special care must still be taken, because the Euclidean theory a priori has boundaries, so that appropriate boundary conditions are required for unitarity. Reflecting boundary conditions would reinstate a Hartle-Hawking-like solution in the Lorentzian regime. To exclude an incoming wave in the Lorentzian domain one must allow a semi-infinite tower of spheres in the Euclidean region, wave packets traveling through successive spheres for half an eternity in unimodular time. Such a “Sisyphus” boundary condition no longer even vaguely resembles Vilenkin’s original proposal.
Date Issued
2023-07-15
Date Acceptance
2023-07-11
Citation
Physical Review D, 2023, 108 (2)
ISSN
2470-0010
Publisher
American Physical Society
Journal / Book Title
Physical Review D
Volume
108
Issue
2
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.
Published by the American Physical Society
Published by the American Physical Society
License URL
Identifier
https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:001054383800002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=a2bf6146997ec60c407a63945d4e92bb
Subjects
Astronomy & Astrophysics
Physical Sciences
Physics
Physics, Particles & Fields
QUANTUM
Science & Technology
TIME
Publication Status
Published
Article Number
023526
Date Publish Online
2023-07-26