Vacuum Bubble in an Inhomogeneous Cosmology

TL;DR

This paper investigates how vacuum bubbles evolve within an inhomogeneous cosmological background, revealing that local inhomogeneities have minimal impact on bubble dynamics, with implications for understanding the landscape of possible universes.

Contribution

It introduces a model for bubble propagation in an inhomogeneous universe satisfying energy conditions, showing inhomogeneities minimally affect bubble evolution.

Findings

Bubble evolution largely unaffected by local inhomogeneities.

Sample profiles satisfying energy conditions show consistent bubble dynamics.

Model serves as a toy for studying inhomogeneity effects on inflation.

Abstract

We study the propagation of bubbles of new vacuum in a radially inhomogeneous Lemaitre-Tolman-Bondi background that includes a cosmological constant. This exemplifies the classical evolution of a tunneling bubble through a metastable state with curvature inhomogeneities, and will be relevant in the context of the Landscape. We demand that the matter profile in the LTB background satisfy the weak energy condition. For sample profiles that satisfy this restriction, we find that the evolution of the bubble (in terms of the physically relevant coordinates intrinsic to the shell) is largely unaffected by the prsence of local inhomogeneities. Our setup should also be a useful toy model for capturing the effects of ambient inhomogeneities on an inflating region.