Primordial non-Gaussianity as a saviour for PBH overproduction in SIGWs generated by Pulsar Timing Arrays for Galileon inflation

TL;DR

This paper explores how negative local non-Gaussianity in Galileon inflation can suppress primordial black hole overproduction while generating scalar-induced gravitational waves consistent with pulsar timing array observations.

Contribution

It demonstrates that negative non-Gaussianity in Galileon inflation prevents PBH overproduction and explains PTA data through SIGWs.

Findings

Negative non-Gaussianity suppresses PBH formation.

Galileon inflation produces SIGWs matching PTA observations.

Avoids PBH overproduction while fitting gravitational wave data.

Abstract

We investigate the explicit role of negative local non-Gaussianity, $f_{\rm NL}$, in suppressing the abundance of primordial black holes (PBHs) in the single-field model of Galileon inflation. PBH formation requires significantly enhancing the scalar power spectrum, which greatly affects their abundance. The associated frequencies in the nHz regime are also sensitive to the generation of scalar-induced gravitational waves (SIGWs) which may explain the current data from the pulsar timing arrays (PTAs). Our analysis using the threshold statistics on the compaction function demonstrates that Galileon theory not only avoids PBH overproduction using the curvature perturbation enhancements that give $f_{\rm NL} \sim {\cal O}(-6)$, but also generates SIGWs that conform well with the PTA data.