Update on gravitational wave signals from post-inflationary phase transitions

TL;DR

This paper reviews gravitational wave signals from early universe phase transitions post-inflation, emphasizing the impact of matter domination and constraints on high-frequency spectrum features.

Contribution

It provides a quantitative analysis of how matter domination affects gravitational wave signals and constrains the high-frequency spectrum based on bubble scale considerations.

Findings

Matter domination influences gravitational wave signal features.

High-frequency spectrum constrained by bubble scale and mean free path.

Summary of broad features relevant for high-frequency detectors.

Abstract

In view of recent interest in high-frequency detectors, broad features of gravitational wave signals from phase transitions taking place soon after inflation are summarized. The influence of the matter domination era that follows the slow-roll stage is quantified in terms of two equilibration rates. Turning to the highest-frequency part of the spectrum, we show how it is constrained by the fact that the bubble distance scale must exceed the mean free path.