Leptogenesis, primordial gravitational waves, and PBH-induced reheating

We explore the possibility of producing the observed matter-antimatter asymmetry of the Universe uniquely from the evaporation of primordial black holes (PBHs) that are formed in an inflaton-dominated background. Considering the inflaton <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mo stretchy="false">(</a:mo><a:mi>ϕ</a:mi><a:mo stretchy="false">)</a:mo></a:math> to oscillate in a monomial potential <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>V</e:mi><e:mo stretchy="false">(</e:mo><e:mi>ϕ</e:mi><e:mo stretchy="false">)</e:mo><e:mo>∝</e:mo><e:msup><e:mi>ϕ</e:mi><e:mi>n</e:mi></e:msup></e:math>, we show, it is possible to obtain the desired baryon asymmetry via vanilla leptogenesis from evaporating PBHs of initial mass <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mo>≲</i:mo><i:mn>10</i:mn><i:mtext> </i:mtext><i:mtext> </i:mtext><i:mi mathvariant="normal">g</i:mi></i:math>. We find that the allowed parameter space is heavily dependent on the shape of the inflaton potential during reheating (determined by the exponent of the potential <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"><l:mi>n</l:mi></l:math>), the energy density of PBHs (determined by <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mi>β</n:mi></n:math>), and the nature of the coupling between the inflaton and the Standard Model. To complete the minimal gravitational framework, we also include in our analysis the gravitational leptogenesis setup through inflaton scattering via exchange of graviton, which opens up an even larger window for PBH mass, depending on the background equation of state. We finally illustrate that such gravitational leptogenesis scenarios can be tested with upcoming gravitational wave (GW) detectors, courtesy of the blue-tilted primordial GW with inflationary origin, thus paving a way to probe a PBH-induced reheating together with leptogenesis. Published by the American Physical Society 2024