On the inflationary interpretation of the nHz gravitational-wave background

TL;DR

This paper presents a single-field inflation model with an ultra-slow-roll phase that explains the nHz gravitational-wave background observed by NANOGrav, aligning with cosmological data from Planck and BICEP/Keck.

Contribution

It introduces a novel inflationary model that links ultra-slow-roll dynamics to the generation of a detectable low-frequency gravitational-wave signal.

Findings

The model produces a significant scalar-induced GW signal at nHz frequencies.

It aligns with recent NANOGrav measurements of the low-frequency GW background.

The model is consistent with Planck and BICEP/Keck cosmological constraints.

Abstract

We construct a single-field model of inflation that achieves remarkable agreement with Planck and BICEP/Keck cosmological observations. The model, via the presence of an ultra-slow-roll phase, generates a sizable scalar-induced gravitational wave (GW) signal at nHz frequencies. We elucidate the distinctive features of this signal concerning its connection to the recent measurement of the low-frequency GW background reported by the NANOGrav collaboration.