Junction Conditions of Friedmann-Robertson-Walker Space-Times

TL;DR

This paper classifies junctions of two Friedmann-Robertson-Walker space-times with spherical thin walls, including super-horizon bubbles, and derives a formula for the domain wall's peculiar velocity, expanding understanding of cosmological bubble dynamics.

Contribution

It completes the classification of junctions for super-horizon bubbles and derives a universal formula for the peculiar velocity of domain walls.

Findings

Multiple topology types for super-horizon bubbles are possible.

The sign of extrinsic curvature does not restrict bubble topology.

A general formula for domain wall velocity is provided.

Abstract

We complete a classification of junctions of two Friedmann-Robertson-Walker space-times bounded by a spherical thin wall. Our analysis covers super-horizon bubbles and thus complements the previous work of Berezin, Kuzumin and Tkachev. Contrary to sub-horizon bubbles, various topology types for super-horizon bubbles are possible, regardless of the sign of the extrinsic curvature. We also derive a formula for the peculiar velocity of a domain wall for all types of junction.