Sound Speed Resonance of Gravitational Waves in Gauss-Bonnet-coupled inflation

TL;DR

This paper explores how sound speed resonances in Gauss-Bonnet-coupled inflation can amplify gravitational waves, producing signals detectable by future experiments, with implications for understanding early universe dynamics.

Contribution

It demonstrates the occurrence of sound speed resonance in Gauss-Bonnet inflation and predicts observable gravitational wave signatures from this phenomenon.

Findings

Resonant amplification of tensor modes due to sound speed oscillations.

Potential detection of gravitational wave signals by SKA, DECIGO, and BBO.

Distinctive stochastic gravitational wave background linked to second inflation phase.

Abstract

We demonstrate the occurrence of Sound Speed Resonances (SSR) in Gauss-Bonnet-coupled inflation across a wide range of coupling functions and parameters. After inflation, the damped oscillations of the inflaton around its potential minimum induces damped oscillations of the sound speed of tensor modes, leading to resonant amplification of the latter. Once the inflaton stabilizes around the minimum, the tensor sound speed reduces to unity (speed of light). In the context of multi-field inflation, the sound speed oscillations can be followed by a second phase of inflation, resulting in a distinctive stochastic background of Gravitational Waves (GWs). We show that these GW signals can be probed by upcoming experiments such as $\textbf{SKA}$, $\textbf{DECIGO}$, and $\textbf{BBO}$ depending on the duration of the second inflationary phase.