The cosmic coincidences of primordial-black-hole dark matter

TL;DR

This paper explores how primordial black holes could account for a significant portion of dark matter, linking their formation to baryogenesis and predicting observable gravitational wave signals.

Contribution

It proposes a novel connection between PBH dark matter and baryogenesis through inflationary dynamics, with testable observational predictions.

Findings

PBHs can constitute over 10% of dark matter density.

Inflationary models can produce conditions for PBH formation and baryogenesis simultaneously.

Predicted gravitational wave signals are within observable ranges.

Abstract

If primordial black holes (PBHs) contribute more than 10 percent of the dark matter (DM) density, their energy density today is of the same order as that of the baryons. Such a cosmic coincidence might hint at a mutual origin for the formation scenario of PBHs and the baryon asymmetry of the Universe. Baryogenesis can be triggered by a sharp transition of the rolling rate of inflaton from slow-roll to (nearly) ultraslow-roll phases that produces large curvature perturbations for PBH formation in single-field inflationary models. We show that the baryogenesis requirement drives the PBH contribution to DM, along with the inferred PBH mass range, the resulting stochastic gravitational wave background frequency window, and the associated cosmic microwave background tensor-to-scalar ratio amplitude, into potentially observable regimes.