Gravitational waves from domain walls and their implications

TL;DR

This paper investigates how domain-wall annihilation can produce detectable gravitational waves and contribute to baryogenesis, highlighting the potential for current and future experiments like advanced LIGO to explore these phenomena.

Contribution

It introduces a novel scenario where domain-wall annihilation from a Higgs portal scalar generates observable gravitational waves and baryon asymmetry, with detailed sensitivity analysis.

Findings

Domain-wall annihilation produces gravitational waves detectable by advanced LIGO.

A Higgs portal scalar can stabilize the Higgs potential and form domain walls.

Domain-wall annihilation can generate baryon asymmetry without isocurvature constraints.

Abstract

We evaluate the impact of domain-wall annihilation on the currently ongoing and planned gravitational wave experiments, including a case in which domain walls experience a frictional force due to interactions with the ambient plasma. We show the sensitivity reach in terms of physical parameters, namely, the wall tension and the annihilation temperature. We find that a Higgs portal scalar, which stabilizes the Higgs potential at high energy scales, can form domain walls whose annihilation produces a large amount of gravitational waves within the reach of the advanced LIGO experiment (O5). Domain wall annihilation can also generate baryon asymmetry if the scalar is coupled to either SU(2)$_L$ gauge fields or the $(B-L)$ current. This is a variant of spontaneous baryogenesis, but it naturally avoids the isocurvature constraint due to the scaling behavior of the domain-wall evolution. We delineate the parameter space where the domain-wall baryogenesis works successfully and discuss its implications for the gravitational wave experiments.