Primordial black holes from spectator field bubbles

TL;DR

This paper investigates how false vacuum bubbles formed by spectator fields during inflation can collapse into primordial black holes, potentially explaining some dark matter and generating observable gravitational waves.

Contribution

It introduces a novel mechanism for primordial black hole formation via spectator field bubbles and explores their cosmological implications.

Findings

Primordial black holes can form from collapsing false vacuum bubbles during inflation.

The black hole mass function is constrained to produce at most 1% of dark matter.

The resulting black holes can generate detectable gravitational waves and influence early Universe dynamics.

Abstract

We study the evolution of light spectator fields in an asymmetric polynomial potential. During inflation, stochastic fluctuations displace the spectator field from the global minimum of its potential, populating the false vacuum state and thereby allowing for the formation of false vacuum bubbles. By using a lattice simulation, we show that these bubbles begin to contract once they re-enter the horizon and, if sufficiently large, collapse into black holes. This process generally results in the formation of primordial black holes, which, due to the specific shape of their mass function, are constrained to yield at most 1% of the total dark matter abundance. However, the resulting population can source gravitational wave signals observable at the LIGO-Virgo experiments, provide seeds for supermassive black holes or cause a transient matter-dominated phase in the early Universe.