Particle production during inflation and gravitational waves detectable by ground-based interferometers

TL;DR

This paper explores how particle production during inflation can create detectable features in the primordial gravitational wave spectrum, potentially observable by ground-based and space interferometers like LIGO and LISA.

Contribution

It introduces the idea that particle production, especially of vectors and electromagnetic fields, can generate detectable gravitational wave signals during inflation, a novel mechanism compared to standard models.

Findings

Vector particle production can create a detectable gravitational wave bump.

Electromagnetic fields amplified by an axion-like inflaton produce chiral gravitational waves detectable by LIGO.

Explosive scalar particle production does not significantly affect the tensor spectrum.

Abstract

Inflation typically predicts a quasi scale-invariant spectrum of gravitational waves. In models of slow-roll inflation, the amplitude of such a background is too small to allow direct detection without a dedicated space-based experiment such as the proposed BBO or DECIGO. In this paper we note that particle production during inflation can generate a feature in the spectrum of primordial gravitational waves. We discuss the possibility that such a feature might be detected by ground-based laser interferometers such as Advanced LIGO and Advanced Virgo, which will become operational in the next few years. We also discuss the prospects of detection by a space interferometer like LISA. We first study gravitational waves induced by nonperturbative, explosive particle production during inflation: while explosive production of scalar quanta does not generate a significant bump in the primordial tensor spectrum, production of vectors can. We also show that chiral gravitational waves produced by electromagnetic fields amplified by an axion-like inflaton could be detectable by Advanced LIGO.