Primordial black holes from the ultraslow-roll phase in the inflaton--curvaton mixed field inflation

TL;DR

This paper investigates how an inflaton--curvaton mixed field model with an ultraslow-roll phase can produce primordial black holes that potentially account for all dark matter, highlighting the impact of the curvaton on non-Gaussianity and inflationary dynamics.

Contribution

It introduces a novel inflaton--curvaton model with an ultraslow-roll phase that enhances PBH formation and affects non-Gaussianity, expanding the understanding of early universe inflation scenarios.

Findings

Can produce PBHs around 10^{-14} M_sun as dark matter candidates.

Curvaton significantly influences primordial non-Gaussianity.

Model remains consistent with observational constraints.

Abstract

Primordial black holes (PBHs) are a promising candidate for dark matter, as they can form in the very early universe without invoking new particle physics. This work explores PBH formation within a curvaton scenario featuring an ultraslow-roll (USR) phase. An inflaton--curvaton mixed field model is presented, where the inflaton drives early inflation and then transits into the USR phase, amplifying the small-scale curvature perturbation. During inflation, the curvaton generates entropy perturbation, which later converts into curvature perturbation after the curvaton decays in the radiation-dominated era. Using the $\delta N$ formalism, we compute the power spectrum of the total primordial curvature perturbation and analyze the relevant non-Gaussianity. Our results show that adding a curvaton field not only has a significant impact on primordial non-Gaussianity, but also introduces more complex inflationary dynamics, even saving the inflaton potentials that generate too low scalar spectral indices. Our model can produce PBHs with mass around $10^{-14}\,M_\odot$ that account for all dark matter, while remaining consistent with current observational constraints.