Signatures of Superstring theory in NANOGrav

Abstract

In this Letter, we extract for the first time signatures of Superstring theory in the recently released NANOGrav data. We concentrate on the primordial gravitational wave (GW) spectrum induced by the gravitational potential of a population of primordial black holes (PBHs) generated in the framework of no-scale Supergravity. In particular, working within Wess-Zumino type no-scale Supergravity we find naturally-realised inflection-point inflationary potentials, which can give rise to the formation of microscopic PBHs triggering an early matter-dominated era (eMD) and evaporating before Big Bang Nucleosythesis (BBN). Remarkably, we obtain an abundant production of gravitational waves, whose profile is quite distinctive, characterized by a strong oscillatory pattern and being in strong agreement with NANOGrav data. Hence, such a signal can act as a potential signature of no-scale Supergravity and Superstring theory at the current and near-future GW observations.Comment: Minor changes: new references and small discussion adde