Primordial black holes and scalar induced gravitational waves from the $E$ model with a Gauss-Bonnet term

TL;DR

This paper explores an inflationary $E$ model with Gauss-Bonnet coupling, demonstrating its potential to produce primordial black holes and scalar induced gravitational waves that could explain various astrophysical phenomena and signals.

Contribution

It introduces a novel inflationary $E$ model with Gauss-Bonnet coupling, analyzing its effects on primordial black hole formation and gravitational wave production, including non-Gaussianity impacts.

Findings

PBHs with specific masses can explain LIGO-Virgo events and dark matter.

SIGWs can account for the NANOGrav signal.

Non-Gaussianity enhances PBH formation, affecting abundance estimates.

Abstract

We study an inflationary $E$ model with the Gauss-Bonnet coupling, which can enhance the curvature perturbation at small scales and thus produce a significant abundance of primordial black holes (PBHs) and detectable scalar induced gravitational waves (SIGWs). PBHs from the $E$ model with mass $30M_{\odot}$, $10^{-5}M_{\odot}$, and $10^{-12}M_{\odot}$ can explain the LIGO-Virgo events, the ultrashort-timescale microlensing events in the OGLE data, and all dark matter, respectively. SIGWs produced by the $E$ model can account for the recent NANOGrav signal. We also compute the primordial non-Gaussianity and discuss its impact on PBHs and SIGWs. The probability distribution of density contrast is modified to be right-tailed, which we find prompts the formation of PBHs, so that the abundance of PBHs is underestimated with Gaussian approximation. On the contrary, the fractional energy density of SIGWs is hardly affected.