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arXiv · 2106.09751

Midisuperspace foam and the cosmological constant

S. Carlip
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Abstract

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 $\Lambda$ 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.

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S. Carlip. 2021-06-17. Midisuperspace foam and the cosmological constant. https://doi.org/10.1088/1361-6382%2Fac3a9f

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