Resonant features in the stochastic gravitational wave background

TL;DR

This paper investigates how resonant features in the scalar power spectrum during inflation produce distinctive oscillatory patterns in the stochastic gravitational wave background, aiding future data analysis.

Contribution

It introduces a semi-analytical method to model the gravitational wave spectrum resulting from resonant scalar features, extending previous work on sharp features.

Findings

Oscillations in scalar spectrum induce modulated gravitational wave signals.

The gravitational wave spectrum shows a superposition of two oscillatory components.

Results serve as templates for reconstructing inflationary features from future gravitational wave data.

Abstract

We analyse the post-inflationary contribution to the stochastic gravitational wave background due to a resonant feature in the scalar power spectrum, which is characterised by an oscillation in $\log(k)$, complementing our previous work arXiv:2012.02761 on sharp features. Primordial features signal departures of inflation from the single-field slow-roll paradigm and are motivated by embeddings of inflation in high energy physics. We find that the oscillation in the scalar power spectrum leads to a corresponding modulation in the gravitational wave spectrum that can be understood as a superposition of two oscillatory pieces, one with the original frequency of the scalar oscillations, and one with double frequency. For oscillations with slowly-varying amplitude this oscillatory part can be computed semi-analytically. Our results can be used as templates for the reconstruction of the signal from future data and permit extracting information about the small scale scalar power spectrum from measurements of the stochastic gravitational wave background.