Multiverse rate equation including bubble collisions

TL;DR

This paper extends the multiverse rate equation to include bubble collisions and classical transitions, exploring their impact on vacuum structure and implications for cosmological issues.

Contribution

The authors generalize the multiverse rate equation to incorporate bubble collisions and classical transitions, providing a more comprehensive model of vacuum dynamics.

Findings

Classical transitions can alter the hierarchy of vacuum volume fractions.

Including bubble collisions affects the stability and distribution of vacua.

Implications for the likelihood of our vacuum being formed by classical transitions.

Abstract

The volume fractions of vacua in an eternally inflating multiverse are described by a coarse-grain rate equation, which accounts for volume expansion and vacuum transitions via bubble formation. We generalize the rate equation to account for bubble collisions, including the possibility of classical transitions. Classical transitions can modify the details of the hierarchical structure among the volume fractions, with potential implications for the staggering and Boltzmann-brain issues. Whether or not our vacuum is likely to have been established by a classical transition depends on the detailed relationships among transition rates in the landscape.