Formation of primordial black holes after Starobinsky inflation

TL;DR

This paper demonstrates that a modified gravity model can produce primordial black holes with masses up to 10^{19} g during double inflation, potentially contributing to dark matter, while aligning with cosmic microwave background observations.

Contribution

It introduces a single-field $F(R)$ gravity model capable of generating large primordial black holes during inflation, extending previous models to include double inflation scenarios.

Findings

Enhanced scalar curvature perturbations beyond Hawking limit

Primordial black holes can survive and contribute to dark matter

Model aligns with cosmic microwave background data within 3σ

Abstract

We adapted the Appleby-Battye-Starobinsky model of $F(R)$ gravity towards describing double cosmological inflation and formation of primordial black holes with masses up to $10^{19}$ g in the single-field model. We found that it is possible to get an enhancement of the power spectrum of scalar curvature perturbations to the level beyond the Hawking (black hole evaporation) limit of $10^{15}$ g, so that the primordial black holes resulting from gravitational collapse of those large primordial perturbations can survive in the present universe and form part of cold dark matter. Our results agree with the current measurements of cosmic microwave background radiation within $3\sigma$ but require fine-tuning of the parameters.