Midisuperspace foam and the cosmological constant

Wheeler’s conjectured ‘spacetime foam’—large quantum fluctuations of spacetime at the Planck scale—could have important implications for quantum gravity, perhaps even explaining why the cosmological constant seems so small. Here I explore this problem in a midisuperspace model consisting of metrics...

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Bibliographic Details
Published in:Classical and quantum gravity 2022-01, Vol.39 (2), p.25012
Main Author: Carlip, S
Format: Article
Language:English
Subjects:
Astronomy & Astrophysics
cosmological constant
midisuperspace
minisiperspace
Physics
quantum fluctuations of geometry
quantum gravity
spacetime foam
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Summary:Wheeler’s conjectured ‘spacetime foam’—large quantum fluctuations of spacetime at the Planck scale—could have important implications for quantum gravity, perhaps even explaining why the cosmological constant seems so small. Here I explore this problem in a midisuperspace model consisting of metrics with local spherical symmetry. Classically, an infinite class of ‘foamy’ initial data can be constructed, in which cancellations between expanding and contracting regions lead to a small average expansion even if Λ is large. Quantum mechanically, the model admits corresponding stationary states, for which the probability current is also nearly zero. These states appear to describe a self-reproducing spacetime foam with very small average expansion, effectively hiding the cosmological constant.
ISSN:0264-9381
1361-6382
DOI:10.1088/1361-6382/ac3a9f