Induced Gravitational Waves from Non-attractor Inflation and NANOGrav data

TL;DR

This paper explores how scalar-induced gravitational waves generated during a non-attractor inflation phase can explain NANOGrav data, analyzing model predictions for gravitational wave signals and non-Gaussianity.

Contribution

It introduces a three-phase inflation model with a non-attractor phase and studies its gravitational wave and non-Gaussianity predictions relevant to pulsar timing array observations.

Findings

Model predicts gravitational wave signals compatible with NANOGrav data

Non-Gaussianity parameter $f_{NL}$ is calculated for the setup

Predictions vary with sound speed and transition sharpness

Abstract

In this paper, we investigate the scalar-induced gravitational waves in single-field non-attractor inflation for the Pulsar Timing Arrays data. Our model comprises three phases of inflation: the first and third phases are slow-roll inflation, while the second phase is a period of non-attractor inflation. We analyze the model's predictions for various values of the sound speed $c_s$ and examine the sharp transitions to the final attractor phase. Furthermore, we study the model's predictions for NANOGrav observations and future gravitational wave observations. We also calculate the non-Gaussianity parameter $f_{NL}$ for the non-attractor setup with a general sound speed and the sharpness parameter.