Gravitational waves in preheating

TL;DR

This paper investigates how gravitational waves evolve during the preheating phase after inflation, showing they carry imprints of preheating despite not being strongly amplified.

Contribution

It provides a covariant analysis of gravitational wave evolution during preheating, highlighting how tensor modes encode information about this epoch.

Findings

Super-Hubble tensor modes are not strongly amplified during preheating.

Gravitational waves carry an imprint of preheating in the Weyl tensor.

The Weyl tensor offers a covariant way to describe gravitational waves.

Abstract

We study the evolution of gravitational waves through the preheating era that follows inflation. The oscillating inflaton drives parametric resonant growth of scalar field fluctuations, and although super-Hubble tensor modes are not strongly amplified, they do carry an imprint of preheating. This is clearly seen in the Weyl tensor, which provides a covariant description of gravitational waves.