The Dual Primordial Black Hole Formation Scenario

TL;DR

This paper introduces a new two-stage inflation model where two distinct populations of primordial black holes form at different epochs, potentially explaining dark matter and producing detectable gravitational wave signatures.

Contribution

It proposes a novel dual PBH formation mechanism in a three-phase inflation scenario, linking PBH formation, reheating, and dark matter within a unified framework.

Findings

Distinctive gravitational wave signatures predicted for future detection

Reheating of the universe via ultralight PBH evaporation

Formation of dark matter PBHs after inflation

Abstract

We report a novel mechanism where two families of primordial black holes (PBHs) may form at nearly the same comoving scales but at two different epochs. It is realized in two-stage inflation where a non-inflationary stage is sandwiched by the two inflationary stages. In this case, smaller PBHs form when the comoving scale of interest re-enters the horizon during the break period, and larger PBHs form when the scale re-enters the horizon after inflation. This mechanism may realize both reheating of the universe through the evaporation of ultralight PBHs formed during the break stage and the dark matter by those formed after inflation. We show that this scenario may give rise to a distinctive signature in the stochastic gravitational wave background that can be tested by the near-future gravitational wave observatories such as LISA and DECIGO. Our work thus provides a unified observational window into the physics of inflation, reheating, and dark matter.