Gravitational waves from colliding vacuum bubbles in gauge theories

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 ${\Omega }_{\mathrm{GW}}\propto {\omega }^{2.3}$ at low frequencies and ${\Omega }_{\mathrm{GW}}\propto {\omega }^{-2.4}$ at high frequencies, marking a significant deviation from the popular envelope approximation.

Comments: 10 pages, 5 figures. fixed a small mistake in the computation of the GW spectrum, minor changes in the results