Primordial Black Holes from CDM Isocurvature Perturbations

TL;DR

This paper demonstrates that primordial black holes can form from large isocurvature perturbations in cold dark matter, providing a new method to constrain such perturbations across various scales.

Contribution

It introduces a novel procedure to compute black hole abundance from matter-only universe perturbations and translates observational constraints into model-independent limits.

Findings

Constraints on dark matter isocurvature perturbations weaken slowly on small scales.

Primordial black holes can originate from CDM isocurvature fluctuations.

The new method allows for broad scale analysis of perturbation constraints.

Abstract

We show that primordial black holes can be produced from the collapse of large isocurvature perturbations of the cold dark matter. We develop a novel procedure to compute the resulting black hole abundance by studying matched perturbations of matter-only universes, and we use our procedure to translate observational constraints on black hole abundances into model-independent constraints on cold dark matter isocurvature perturbations over a wide range of scales. The constraint on the typical amplitude of the primordial perturbations weakens slightly slower than linearly on small scales.