Gravitational waves from the electroweak phase transition

TL;DR

This paper investigates gravitational wave production during the electroweak phase transition in various Standard Model extensions, analyzing bubble dynamics, turbulence, and detectability prospects for spaceborne detectors like LISA.

Contribution

It provides a comprehensive analysis of gravitational wave signals from different electroweak phase transition models, including bubble wall dynamics and turbulence effects.

Findings

Runaway bubble walls are fine-tuned and rare.

Turbulence generally produces stronger gravitational wave signals than bubble collisions.

Detectable signals are possible in models with strongly coupled scalars at around 10^{-4} Hz.

Abstract

We study the generation of gravitational waves in the electroweak phase transition. We consider a few extensions of the Standard Model, namely, the addition of scalar singlets, the minimal supersymmetric extension, and the addition of TeV fermions. For each model we consider the complete dynamics of the phase transition. In particular, we estimate the friction force acting on bubble walls, and we take into account the fact that they can propagate either as detonations or as deflagrations preceded by shock fronts, or they can run away. We compute the peak frequency and peak intensity of the gravitational radiation generated by bubble collisions and turbulence. We discuss the detectability by proposed spaceborne detectors. For the models we considered, runaway walls require significant fine tuning of the parameters, and the gravitational wave signal from bubble collisions is generally much weaker than that from turbulence. Although the predicted signal is in most cases rather low for the sensitivity of LISA, models with strongly coupled extra scalars reach this sensitivity for frequencies $f\sim 10^{-4}\,\mathrm{Hz}$, and give intensities as high as $h^2\Omega_{\mathrm{GW}}\sim 10^{-8}$.