Gravitational waves from gauge preheating

TL;DR

This paper investigates the production of gravitational waves during gauge preheating after inflation, highlighting their potential detectability and unique polarization features, and explores implications for matter-antimatter asymmetry.

Contribution

It provides the first detailed analysis of gravitational wave signatures from Abelian gauge preheating with both scalar and pseudoscalar inflaton models, including polarization and leptogenesis.

Findings

Gravitational waves are efficiently produced during preheating.

The resulting gravitational wave spectrum can be helically polarized.

Predicted signals may be detectable by future CMB experiments.

Abstract

We study gravitational wave production during Abelian gauge-field preheating following inflation. We consider both scalar and pseudoscalar inflaton models coupled directly to Abelian gauge fields via either a dilatonic coupling to the gauge-field kinetic term or an axial coupling to a Chern-Simons term. In both cases gravitational waves are produced efficiently during the preheating phase, with a signature louder than most cosmological signals. These gravitational waves can contribute to the radiation energy budget of Universe at a level which will be probed by upcoming cosmic microwave background experiments through $N_{\rm eff}$. For axially coupled fields the resulting gravitational wave spectrum is helically polarized---a unique feature that can be used to differentiate it from other stochastic gravitational wave backgrounds. We compute the gravitational topological charge and demonstrate that gauge preheating following axion inflation may be responsible for the matter-antimatter asymmetry of the Universe via gravitational leptogenesis.