Gravitational waves from resonant amplification of curvature perturbations during inflation

TL;DR

This paper explores how parametric resonance during inflation amplifies curvature perturbations, leading to potential observable gravitational waves and primordial black holes, with distinctive spectral features detectable by future space-based interferometers.

Contribution

It introduces a detailed analysis of stochastic gravitational wave backgrounds generated during inflation and radiation era, highlighting unique spectral oscillations and amplitude differences.

Findings

Peak of inflation-produced GWs is higher but at lower frequency.

Oscillating spectral feature in ultraviolet region during inflation.

Both GW backgrounds are detectable by future space-based interferometers.

Abstract

Parametric resonance in a single-field inflationary model with a periodic structure on the potential gives rise to curvature perturbations with large amplitudes on small scales, which could result in observable primordial black holes (PBHs) and concomitant gravitational waves (GWs) induced by curvature perturbations in the radiation-dominated era. In such a model, GWs associated with the PBH formation were investigated in Ref. [1]. In this paper, we consider a stochastic GW background sourced by inflaton perturbations resonantly amplified during inflation. We compute the energy spectra of induced GWs produced both during inflation and in the radiation-dominated era, and find that the peak of the energy spectrum of the former is much higher than that of the latter, but is located at a lower frequency. Moreover, the energy spectrum of induced GWs produced during inflation exhibits a unique oscillating character in the ultraviolet region. Both the stochastic GW backgrounds are expected to be detected by future space-based laser interferometers.