Gravitational waves from colliding vacuum bubbles in gauge theories

TL;DR

This paper investigates gravitational wave production during strongly supercooled phase transitions in gauge theories, revealing a decay pattern of the GW source and a distinctive spectrum shape that deviates from previous models.

Contribution

It introduces a new decay law for the GW source in gauge theories and provides detailed spectrum predictions based on lattice and many-bubble simulations.

Findings

GW source decays as R^{-3} after bubble collisions

GW spectrum follows a power law with exponents 2.3 and -2.4 at low and high frequencies

Deviation from the envelope approximation in spectrum shape

Abstract

We study production of gravitational waves (GWs) in strongly supercooled cosmological phase transitions in gauge theories. We extract from two-bubble lattice simulations the scaling of the GW source, and use it in many-bubble simulations in the thin-wall limit to estimate the resulting GW spectrum. We find that in presence of the gauge field the GW source decays with bubble radius as $\propto R^{-3}$ after collisions. This leads to a GW spectrum that follows $\Omega_{\rm GW} \propto \omega^{2.3}$ at low frequencies and $\Omega_{\rm GW} \propto \omega^{-2.4}$ at high frequencies, marking a significant deviation from the popular envelope approximation.