Probing Reheating with Gravitational Waves from Graviton Bremsstrahlung

TL;DR

This paper explores how gravitational waves generated by graviton bremsstrahlung during inflationary reheating can reveal details about the reheating process, with potential detection prospects in future GW observatories.

Contribution

It introduces a novel mechanism for primordial GW production during reheating and analyzes how GW spectra encode information about the inflaton potential and couplings.

Findings

GW spectrum features depend on reheating dynamics

Next-generation GW detectors can probe high-frequency GW signals

Bremsstrahlung-induced GWs can reveal reheating details

Abstract

In this talk, based on arXiv:2301.11345, arXiv:2305.16388, arXiv:2311.12694, we discuss the production of primordial gravitational waves (GW) sourced by graviton bremsstrahlung during inflationary reheating. For reheating, we consider inflaton decays and annihilations into pairs of bosons or fermions, assuming an inflaton $\phi$ that oscillates around a generic monomial potential $V(\phi) \propto \phi^n$. The GW spectrum exhibits distinct features depending on the underlying reheating dynamics, which is controlled by the inflaton potential and the type of coupling between the inflaton and the matter fields. We show that the produced stochastic GW background could be probed in next-generation GW detectors, especially at high frequencies. We further highlight the potential of bremsstrahlung-induced GW to probe the underlying dynamics of reheating.