Impact of memory-burdened primordial black holes on high-scale leptogenesis

We explore the impact of the backreaction of evaporation on the quantum state of primordial black holes (PBHs), known as “memory burden,” on the baryon asymmetry production in the Universe through high-scale leptogenesis. Focusing on PBH masses ranging from 1 to 1000 g, we investigate the interplay between the nonthermal production of heavy sterile neutrinos and the entropy injection within this nonstandard cosmological framework. By assuming appropriate values for the memory-burden parameters, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>q</a:mi><a:mo>=</a:mo><a:mn>1</a:mn><a:mo>/</a:mo><a:mn>2</a:mn></a:math> and <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>k</c:mi><c:mo>=</c:mo><c:mn>1</c:mn></c:math>, we derive mutual exclusion limits between PBHs and thermal leptogenesis in the mixed parameter space. Our analysis reveals that the primary contribution of PBHs to baryon asymmetry stems from entropy injection. Indeed, we find that, different from earlier studies based on the semiclassical Hawking evaporation, the memory-burden effect suppresses the nonthermal source term in the PBH mass range explored. This has significant implications for understanding baryogenesis in such alternative cosmological scenarios.