Pulsar timing array observations as possible hints for nonsingular cosmology

TL;DR

This paper proposes a Genesis-inflation model that explains recent pulsar timing array observations of a stochastic gravitational wave background as primordial GWs, while addressing the initial singularity problem and predicting testable spectral features.

Contribution

It introduces a novel Genesis-inflation model that accounts for PTA signals and resolves the initial singularity issue in cosmology.

Findings

The model explains PTA-observed SGWB as primordial GWs with a blue-tilted spectrum.

Predicts distinctive SGWB spectral features for future space-based GW experiments.

Addresses the initial singularity problem in inflationary cosmology.

Abstract

Recent pulsar timing array (PTA) experiments have reported strong evidence of the stochastic gravitational wave background (SGWB). If interpreted as primordial gravitational waves (GWs), the signal favors a strongly blue-tilted spectrum. Consequently, the nonsingular cosmology, which is able to predict a strongly blue-tilted GW spectrum with $n_T \simeq 2$ on certain scales, offers a potential explanation for the observed SGWB signal. In this paper, we present a Genesis-inflation model capable of explaining the SGWB signal observed by the PTA collaborations while also overcoming the initial singularity problem associated with the inflationary cosmology. Furthermore, our model predicts distinctive features in the SGWB spectrum, which might be examined by forthcoming space-based gravitational wave experiments.