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

Understand

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.