Primordial black holes from modified supergravity

TL;DR

This paper explores how modified supergravity models can naturally produce primordial black holes during a two-stage inflation process, potentially explaining dark matter with PBHs in a specific mass range.

Contribution

It introduces a novel two-field inflation model within modified supergravity that predicts PBH formation and their contribution to dark matter.

Findings

PBHs with masses between 10^{16} g and 10^{20} g can form efficiently.

The model aligns with inflationary observational constraints.

PBH abundance could account for a significant fraction of dark matter.

Abstract

The modified supergravity approach is applied to describe a formation of Primordial Black Holes (PBHs) after Starobinsky inflation. Our approach naturally leads to the two-(scalar)-field attractor-type double inflation, whose first stage is driven by scalaron and whose second stage is driven by another scalar field which belongs to a supergravity multiplet. The scalar potential and the kinetic terms are derived, the vacua are studied, and the inflationary dynamics of those two scalars is investigated. We numerically compute the power spectra and we find the ultra-slow-roll regime leading to an enhancement (peak) in the scalar power spectrum. This leads to an efficient formation of PBHs. We estimate the masses of PBHs and we find their density fraction (as part of Dark Matter). We show that our modified supergravity models are in agreement with inflationary observables, while they predict the PBH masses in a range between $10^{16}$ g and $10^{20}$ g. In this sense, modified supergravity provides a natural top-down approach for explaining and unifying the origin of inflation and the PBHs Dark Matter.