Bubbles kick off primordial black holes to form more binaries

TL;DR

This paper uses numerical relativity to simulate primordial black hole and bubble wall collisions, revealing effects like mass growth, gravitational waves, and increased binary formation rates, impacting observational constraints.

Contribution

First simulation of PBH-bubble wall collisions with full numerical relativity, showing significant effects on PBH evolution and binary formation.

Findings

PBH mass increases due to collisions

Generation of gravitational waves from collisions

Enhanced PBH binary formation rate

Abstract

Primordial black holes (PBHs) may form before cosmological first-order phase transitions, leading to inevitable collisions between PBHs and bubble walls. In this Letter, we have simulated for the first time the co-evolution of an expanding scalar wall passing through a black hole with full numerical relativity. This black hole-bubble wall collision yields multiple far-reaching phenomena, including the PBH mass growth, gravitational wave radiations, and momentum recoil that endows PBHs with additional velocities, approximately doubling the formation rate for PBH binaries and hence strengthening the observational constraints on the PBH abundances.