Dark sector production and baryogenesis from not quite black holes * *Work of U.A. is supported in part by the Chinese Academy of Sciences President's International Fellowship Initiative (PIFI) (2020PM0019) and the Institute of High Energy Physics, Chinese Academy of Sciences (Y9291120K2). J.R. is supported by the Institute of High Energy Physics (Y9291120K2)

Abstract

Primordial black holes have been considered attractive dark matter candidates, whereas some of the predictions rely heavily 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 provide a solution to the information loss problem but also naturally result in stable remnants. Previously, we have considered primordial 2-2-hole remnants as dark matter. Owing to the strong constraints from a novel phenomenon associated with remnant mergers, only small remnants with mass approximate to the Planck mass can constitute all dark matter. In this paper, we examine the scenario in which 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 sufficiently light 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 observe that baryogenesis through direct B-violating decays or through leptogenesis can both be realized. Overall, the viable parameter space for the Planck remnant scenario is similar to that of primordial black holes with Planck remnants. However, heavier remnants result in different predictions, and the viable parameter space remains large even when the remnant abundance is small.