Primordial black holes and secondary gravitational waves from natural inflation

TL;DR

This paper explores how natural inflation models can produce primordial black holes as dark matter candidates and generate secondary gravitational waves, with specific mass and frequency predictions testable by future observatories.

Contribution

It demonstrates a mechanism within natural inflation to enhance curvature perturbations, leading to PBH dark matter and detectable scalar induced gravitational waves.

Findings

PBH dark matter can have masses around 10^{-13} solar masses.

Scalar induced gravitational waves peak at mHz, 10^{-6} Hz, and nHz frequencies.

PBHs with 10^{-13} solar masses can constitute almost all dark matter.

Abstract

The production of primordial black hole (PBH) dark matter (DM) and the generation of scalar induced secondary gravitational waves by using the enhancement mechanism with a peak function in the non-canonical kinetic term in natural inflation is discussed. We show explicitly that the power spectrum for the primordial curvature perturbation can be enhanced at $10^{12}$ Mpc$^{-1}$, $10^{8}$ Mpc$^{-1}$ and $10^{5}$ Mpc$^{-1}$ by adjusting the model parameters. With the enhanced primordial curvature perturbations, we show the production of PBH DM with peak masses around $10^{-13}\ M_{\odot}$, the Earth's mass and the stellar mass, and the generation of scalar induced gravitational waves (SIGWs) with peak frequencies around mHz, $10^{-6}$ Hz and nHz, respectively. The PBHs with the mass scale $10^{-13}\ M_{\odot}$ can make up almost all the DM and the associated SIGWs is testable by spaced based gravitational wave observatory.