Primordial black hole formation by vacuum bubbles

TL;DR

This paper investigates how vacuum bubbles during inflation can lead to various black hole formations, including primordial black holes and baby universes, with a broad mass spectrum that could explain supermassive black holes and LIGO events.

Contribution

The study introduces numerical simulations of vacuum bubble evolution post-inflation, revealing a wide mass spectrum of resulting black holes and potential connections to observed astrophysical phenomena.

Findings

Black holes form with a broad mass spectrum spanning many orders of magnitude.

Supercritical bubbles can create baby universes connected by wormholes that turn into black holes.

Black holes from this process could seed supermassive black holes and explain LIGO observations.

Abstract

Vacuum bubbles may nucleate during the inflationary epoch and expand, reaching relativistic speeds. After inflation ends, the bubbles are quickly slowed down, transferring their momentum to a shock wave that propagates outwards in the radiation background. The ultimate fate of the bubble depends on its size. Bubbles smaller than certain critical size collapse to ordinary black holes, while in the supercritical case the bubble interior inflates, forming a baby universe, which is connected to the exterior region by a wormhole. The wormhole then closes up, turning into two black holes at its two mouths. We use numerical simulations to find the masses of black holes formed in this scenario, both in subcritical and supercritical regime. The resulting mass spectrum is extremely broad, ranging over many orders of magnitude. For some parameter values, these black holes can serve as seeds for supermassive black holes and may account for LIGO observations.