Spacetime foam and the cosmological constantConfirmed

by Steve Carlip (University of California, Davis)

Thursday Mar 26, 2026, 2:30 PM → 4:00 PM America/Toronto

PI/4-405 - Bob Room (Perimeter Institute for Theoretical Physics)

Suppose our universe really had a huge cosmological constant.  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.  At the level of initial data, $\Lambda$ can be "hidden" in spacetime foam, rapidly expanding and contracting regions that 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.