Dynamics of false vacuum bubbles in Brans-Dicke theory

TL;DR

This paper investigates the behavior of false vacuum bubbles in Brans-Dicke gravity, revealing that certain field configurations enable expanding bubbles observable from outside, unlike in Einstein gravity.

Contribution

It introduces the dynamics of false vacuum bubbles in Brans-Dicke theory using the thin shell approximation, highlighting conditions for negative tension and observable expansion.

Findings

Negative effective tension occurs for certain field differences.

Expanding false vacuum bubbles are possible in Brans-Dicke theory.

Such bubbles are not allowed in Einstein gravity.

Abstract

We study the dynamics of false vacuum bubbles in the Brans-Dicke theory of gravity by using the thin shell or thin wall approximation. We consider a false vacuum bubble that has a different value for the Brans-Dicke field between the inside false vacuum region and the outside true vacuum region. Within a certain limit of field values, the difference of field values makes the effective tension of the shell negative. This allows new expanding false vacuum bubbles to be seen by the outside observer, which are disallowed in Einstein gravity.