Effects of Early-Universe Inhomogeneity on Bubble Formation: Primordial Black Holes as an Extreme Case

TL;DR

This paper investigates how early-universe inhomogeneities, exemplified by primordial black holes, influence bubble nucleation during phase transitions, potentially affecting cosmic evolution and gravitational wave signals.

Contribution

It introduces a model analyzing the impact of primordial black holes on bubble nucleation rates and the resulting gravitational wave signatures in the early universe.

Findings

Primordial black holes can lower the effective action for bubble nucleation.

Inhomogeneities may lead to non-spherical bubble formation.

Altered nucleation rates could influence phase transition dynamics.

Abstract

Our early Universe is not perfectly homogeneous and it may contain some inhomogeneous sources, which might distort the local spacetime and modify the bubble nucleation rate. Taking the primordial black hole as an extreme example, we investigate the bubble nucleation rate of a first-order phase transition in the vicinity of primordial black holes or other primordial gravitational sources. Our analysis reveals that the presence of primordial black holes can reduce the effective action and might modify the nucleation rate due to their gravitational effects, potentially altering the dynamics of the phase transition in the early universe and producing new gravitational wave signals since the gravitational effects of the primordial black hole or other possible inhomogeneous sources could lead to nucleation of non-spherical symmetric bubbles.