On the fate of vacuum bubbles on matter backgrounds

TL;DR

This paper investigates the evolution of vacuum bubbles during cosmological phase transitions on matter backgrounds, revealing conditions under which bubbles expand or remain static, with implications for early universe models.

Contribution

It introduces a detailed analysis of vacuum bubble dynamics on inhomogeneous matter backgrounds using the thin wall and Israel junction methods, extending previous homogeneous models.

Findings

Bubbles in dust-dominated homogeneous backgrounds cannot expand.

In inhomogeneous dust backgrounds, bubbles can initially expand.

Bubble passage through inhomogeneities appears unnoticed to internal observers.

Abstract

In this letter we discuss cosmological first order phase transitions with de Sitter bubbles nucleating on (inhomogeneous) matter backgrounds. The de Sitter bubble can be a toy model for an inflationary phase of universes like our own. Using the thin wall approximation and the Israel junction method we trace the classical evolution of the formed bubbles within a compound model. We first address homogeneous ambient space (FRW model) and already find that bubbles nucleated in a dust dominated background cannot expand. For an inhomogeneous dust background (LTB model) we describe cases with at least initially expanding bubbles. Yet, an ensuing passage of the bubble wall through ambient curvature inhomogeneities remains unnoticed for observers inside the bubble. Notable effects also for interior observers are found in the case of a rapid background phase transition in a FRW model.