Primordial black hole formation during cosmic phase transitions

TL;DR

This paper demonstrates that cosmic phase transitions, especially the QCD transition, enhance primordial black hole formation, potentially leaving observable signatures in their mass distribution related to the early Universe's thermal history.

Contribution

It introduces the idea that cosmic phase transitions increase PBH formation likelihood and predicts a specific mass peak linked to the QCD transition.

Findings

PBHs form more easily during cosmic phase transitions

A peak in the PBH mass function is expected at 1.9 solar masses due to the QCD transition

The PBH mass function can record the thermal history of the early Universe

Abstract

Primordial black holes (PBHs) may be part of the dark matter. It is shown here that PBHs form more easily during cosmic phase transitions. For approximately scale-invariant primordial curvature fluctuations the PBH mass function may therefore leave a record of the thermal history of the early Universe. In particular a peak is expected on the 1.9 solar mass scale due to the cosmic QCD transition.