Primordial black holes formation and secondary gravitational waves in nonminimal derivative coupling inflation

TL;DR

This paper explores how nonminimal derivative coupling inflation can produce primordial black holes that account for most dark matter and predicts secondary gravitational waves detectable by current or future observatories.

Contribution

It introduces a specific nonminimal derivative coupling model that generates ultra slow-roll inflation, leading to significant PBH formation and associated gravitational wave signals.

Findings

PBHs with mass around 10^{-12} solar masses can make up 96% of dark matter.

The model predicts a gravitational wave energy density peak at about 10^{-8}.

Predicted GW signals are within the sensitivity of some detectors.

Abstract

We study the possibility of the Primordial Black Holes (PBHs) formation with the aim of finding a considerable fraction of Dark Matter (DM), using the gravitationally enhanced friction mechanism which arises from a nonminimal derivative coupling between the scalar field and the gravity. Assuming the nonminimal coupling parameter as a special function of the scalar field and considering the potential of natural inflation, we find three parameter sets that produce a period of ultra slow-roll inflation. This leads to sufficiently large enhancement in the curvature power spectra to form PBHs. We show that under the gravitationally enhanced friction mechanism, PBHs with a mass around ${\cal O}\big(10^{-12}\big)M_\odot$ can constitute around $96\%$ of the total DM and so this class of PBHs can be taken as a great candidate for DM. We further study the secondary Gravitational Waves (GWs) in our setting and show that our model predicts the peak of the present fractional energy density as $\Omega_{GW0} \sim 10^{-8}$ at different frequencies for all the three parameter sets. This value lies well inside the sensitivity region of some GWs detectors at some frequencies, and therefore the observational compatibility of our model can be appraised by the data from these detectors.