Primordial black holes from Q-balls produced in a first-order phase transition

TL;DR

This paper explores how Q-balls formed during a first-order phase transition can collapse into primordial black holes, potentially producing observable multimessenger signals like gravitational waves and gamma-rays, and addressing the Hubble tension.

Contribution

It introduces a novel mechanism linking Q-ball formation in phase transitions to primordial black hole creation with distinctive observational signatures.

Findings

Q-balls can collapse into primordial black holes under certain conditions.

The scenario predicts detectable gravitational waves and gamma-ray signals.

Reheating from the phase transition may help resolve the Hubble tension.

Abstract

We consider the formation of Q-balls in false vacuum remnants during a cosmological first-order phase transition. We find that under certain circumstances Q-balls can collapse to form primordial black holes. This scenario can produce multimessenger signals that may be observed at upcoming experiments, including 1-100 nHz gravitational waves from the phase transition, and gamma-rays emitted from primordial black holes as Hawking radiation and as superradiance. These signals are quite distinctive, and differ markedly from signals expected from Fermi-balls. The reheating of the dark sector from the phase transition may address the Hubble tension.