Tunneling and propagation of vacuum bubbles on dynamical backgrounds

TL;DR

This paper investigates how vacuum bubbles nucleate and propagate in dynamic, non-vacuum backgrounds like FLRW and LTB spacetimes, revealing matter often inhibits bubble expansion and affects interior spacetime minimally.

Contribution

It extends bubble nucleation and propagation analysis to non-vacuum, dynamical backgrounds, providing semi-analytic and numerical results in FLRW and LTB spacetimes.

Findings

Matter often prevents bubble expansion in inhomogeneous backgrounds.

Bubbles that do expand have minimal impact on interior spacetime.

The study offers insights into bubble dynamics in realistic cosmological settings.

Abstract

In the context of bubble universes produced by a first-order phase transition with large nucleation rates compared to the inverse dynamical time scale of the parent bubble, we extend the usual analysis to non-vacuum backgrounds. In particular, we provide semi-analytic and numerical results for the modified nucleation rate in FLRW backgrounds, as well as a parameter study of bubble walls propagating into inhomogeneous (LTB) or FLRW spacetimes, both in the thin-wall approximation. We show that in our model, matter in the background often prevents bubbles from successful expansion and forces them to collapse. For cases where they do expand, we give arguments why the effects on the interior spacetime are small for a wide range of reasonable parameters and discuss the limitations of the employed approximations.