Probing inflationary moduli space with gravitational waves

TL;DR

This paper explores how higher curvature corrections in string theory, specifically the Gauss-Bonnet term, can produce distinctive peaks in the primordial gravitational wave spectrum, potentially detectable by current and future experiments.

Contribution

It demonstrates that a wall-crossing behavior of the modulus field can lead to a Gauss-Bonnet dominated phase, creating observable features in gravitational wave spectra.

Findings

A peak in the gravitational wave spectrum can result from Gauss-Bonnet coupling domination.

Detectability of these gravitational waves with pulsar timing arrays and space interferometers.

Potential to probe string-theoretical corrections through gravitational wave observations.

Abstract

We investigate the spectrum of gravitational waves arising from primordial inflation in the presence of a string-theoretical higher curvature correction, specifically, the Gauss-Bonnet coupling term for the inflaton (modulus) field. We show that if the modulus field exhibits a wall-crossing like behavior in the moduli space, there can be a period of Gauss-Bonnet coupling term domination during the usual slow-roll. This phenomenon is potentially detectable as the gravitational wave spectrum exhibits a characteristic peak caused by the brief domination of the Gauss-Bonnet coupling term. We explore the possibility of measuring such gravitational waves with pulsar timing array experiments such as NANOGrav, and future space-borne interferometers such as LISA, DECIGO, and Taiji.