Gravitational wave signatures of a PBH-generated baryon-dark matter coincidence

Abstract

We propose a new way of probing the nonthermal origin of baryon asymmetry of the Universe (BAU) and dark matter (DM) from evaporating primordial black holes (PBHs) via stochastic gravitational waves (GWs) emitted due to PBH density fluctuations. We adopt a baryogenesis setup where CP-violating out-of-equilibrium decays of a colored scalar, produced nonthermally at late epochs from PBH evaporation, lead to the generation of BAU. The same PBH evaporation is also responsible for nonthermal origin of superheavy DM. Unlike the case of baryogenesis via leptogenesis that necessarily corners the PBH mass to ∼O(1) g, here we can have PBH mass as large as ∼O(107) g due to the possibility of producing BAU directly below sphaleron decoupling temperature. Because of the larger allowed PBH mass we can also have observable GW with mHz-kHz frequencies originating from PBH density fluctuations keeping the model constrained and verifiable at ongoing as well as near future GW experiments like LIGO, BBO, DECIGO, CE, ET etc. Because of the presence of new colored particles and baryon number violation, the model also has complementary detection prospects at laboratory experiments.