Probabilities in the Bousso-Polchinski multiverse

TL;DR

This paper applies a new method to calculate bubble abundances in an eternally inflating universe, revealing a staggered volume distribution for the cosmological constant in the Bousso-Polchinski model, challenging previous assumptions of flatness.

Contribution

It introduces a novel approach to compute bubble abundances and demonstrates that the volume distribution for mbda is staggered, contrasting with prior heuristic flat distribution assumptions.

Findings

The distribution for mbda is staggered, not flat.

Reconciling with observed mbda requires many vacua in the anthropic range.

Previous predictions assuming flat distribution may need revision.

Abstract

Using the recently introduced method to calculate bubble abundances in an eternally inflating spacetime, we investigate the volume distribution for the cosmological constant $\Lambda$ in the context of the Bousso-Polchinski landscape model. We find that the resulting distribution has a staggered appearance which is in sharp contrast to the heuristically expected flat distribution. Previous successful predictions for the observed value of $\Lambda$ have hinged on the assumption of a flat volume distribution. To reconcile our staggered distribution with observations for $\Lambda$, the BP model would have to produce a huge number of vacua in the anthropic range $\Delta\Lambda_A$ of $\Lambda$, so that the distribution could conceivably become smooth after averaging over some suitable scale $\delta\Lambda\ll\Delta\Lambda_A$.