Abstract
In models of baryogenesis based on grand unified theories (GUTs), the baryon asymmetry of the Universe is generated through the $CP$ and baryon number violating, out-of-equilibrium decays of very massive gauge or Higgs bosons in the very early Universe. Recent constraints on the scale of inflation and the subsequent temperature of reheating, however, have put pressure on many such models. In this paper, we consider the role that primordial black holes may have played in the process of GUT baryogenesis. Through Hawking evaporation, black holes can efficiently generate GUT Higgs or gauge bosons, regardless of the masses of these particles or the temperature of the early Universe. Furthermore, in significant regions of parameter space, the black holes evaporate after the electroweak phase transition, naturally evading the problem of sphaleron washout that is normally encountered in GUT models based on $SU(5)$. We identify a wide range of scenarios in which black holes could facilitate the generation of the baryon asymmetry through the production and decays of GUT bosons.
Highlights
One of the most significant open questions in cosmology is how the Universe came to contain more matter than antimatter
In models of baryogenesis based on grand unified theories (GUTs), the baryon asymmetry of the Universe is generated through the CP and baryon number violating, out-of-equilibrium decays of very massive gauge or Higgs bosons in the very early Universe
It is within the context of these challenges for GUT baryogenesis that we consider the role that primordial black holes may have played in this process
Summary
One of the most significant open questions in cosmology is how the Universe came to contain more matter than antimatter. 109–1013 GeV [46,47,48], well below the scale of grand unification, highly suppressing the thermal production of the baryon number and CP violating particles and posing significant problems for many otherwise well-motivated theories of GUT baryogenesis.2 Another challenge faced by many models of GUT baryogenesis comes from the influence of sphalerons on any baryon asymmetry that might be produced. In many GUT models, such as those based on SUð5Þ, no such net B − L is generated, leading to a situation in which the baryon asymmetry is efficiently washed out well before the electroweak phase transition It is within the context of these challenges for GUT baryogenesis that we consider the role that primordial black holes may have played in this process.
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