Implications for First-Order Cosmological Phase Transitions from the Third LIGO-Virgo Observing Run

TL;DR

This paper uses LIGO-Virgo data to set upper limits on gravitational wave backgrounds from first-order cosmological phase transitions and astrophysical sources, refining constraints on early universe models.

Contribution

It provides new upper limits on gravitational wave energy densities from both astrophysical and cosmological sources using multiple observing runs.

Findings

Upper limits on gravitational wave energy density from unresolved binary mergers.

Constraints on gravitational waves from bubble collisions and sound waves in phase transitions.

Inclusion of astrophysical foregrounds is essential for accurate cosmological bounds.

Abstract

We place constraints on the normalized energy density in gravitational waves from first-order strong phase transitions using data from Advanced LIGO and Virgo's first, second and third observing runs. First, adopting a broken power law model, we place $95 \%$ confidence level upper limits simultaneously on the gravitational-wave energy density at 25 Hz from unresolved compact binary mergers, $\Omega_{\rm CBC} < 6.1 \times 10^{-9}$, and strong first-order phase transitions, $\Omega_{\rm BPL} < 4.4 \times 10^{-9}$. The inclusion of the former is necessary since we expect this astrophysical signal to be the foreground of any detected spectrum. We then consider two more complex phenomenological models, limiting at 25 Hz the gravitational-wave background due to bubble collisions to $\Omega_{\rm pt} < 5.0\times 10^{-9}$ and the background due to sound waves to $\Omega_{\rm pt} < 5.8\times10^{-9}$ at $95 \%$ confidence level for phase transitions occurring at temperatures above $10^8$GeV.