Midisuperspacetime foam and the cosmological constant

TL;DR

This paper explores how quantum effects in a spherically symmetric model can hide a large cosmological constant by trapping the wave function in regions of near-zero expansion, challenging classical predictions.

Contribution

It introduces a midisuperspace quantum model demonstrating how inhomogeneities can conceal a large cosmological constant through quantum trapping effects.

Findings

Wave function can be trapped in regions with small average expansion

Quantum effects can hide a large cosmological constant

Inhomogeneous models alter classical cosmological predictions

Abstract

Standard quantum field theory arguments predict an enormous cosmological constant. But what would this mean observationally? For a homogeneous universe the answer is clear, but if the universe is inhomogeneous at the Planck scale, the question becomes more subtle: for a large class of initial data, rapidly expanding and contracting regions coexist and give an average expansion near zero. Classically, such data develop singularities, and we need a quantum description of their evolution. I describe results from a spherically symmetric midisuperspace model, in which the wave function can become trapped for long periods in regions in which the average expansion remains small, effectively hiding a large cosmological constant.