Dark sector production and baryogenesis from not quite black holes

TL;DR

This paper explores how primordial 2-2-holes, a black hole alternative, could produce dark matter particles and baryon asymmetry through evaporation, offering a new perspective on early universe cosmology.

Contribution

It introduces the scenario that primordial 2-2-hole evaporation can account for dark matter and baryogenesis, expanding the understanding of black hole alternatives in cosmology.

Findings

Primordial 2-2-hole evaporation can produce dark matter particles.

Baryogenesis can occur via B-violating decays or leptogenesis from 2-2-hole evaporation.

Viable parameter space similar to primordial black holes with Planck remnants.

Abstract

Primordial black holes have been considered as an attractive dark matter candidate, whereas some of the predictions heavily rely on the near-horizon physics that remains to be tested experimentally. As a concrete alternative, thermal 2-2-holes closely resemble black holes without event horizons. Being a probable endpoint of gravitational collapse, they not only provide a resolution to the information loss problem, but also naturally give rise to stable remnants. Previously, we have considered primordial 2-2-hole remnants as dark matter. Due to the strong constraints from a novel phenomenon associated with remnant mergers, only small remnants with close to the Planck mass can constitute all of dark matter. In this paper, we examine the scenario that the majority of dark matter consists of particles produced by the evaporation of primordial 2-2-holes, whereas the remnant contribution is secondary. The products with light enough mass may contribute to the number of relativistic degrees of freedom in the early universe, which we also calculate. Moreover, 2-2-hole evaporation can produce particles that are responsible for the baryon asymmetry. We find that baryogenesis through direct B-violating decays or through leptogenesis can both be realized. Overall, the viable parameter space for the Planck remnant case is similar to primordial black holes with Planck remnants. Heavier remnants, on the other hand, lead to different predictions, and the viable parameter space remains large even when the remnant abundance is small.