Leptogenesis below the Davidson-Ibarra bound

Abstract

The observed baryon asymmetry of the Universe is suitably created in thermal leptogenesis through the out-of-equilibrium decay of N₁, the lightest of the three heavy singlet neutral fermions which anchor the seesaw mechanism to obtain small Majorana neutrino masses. However, this scenario suffers from the incompatibility of a generic lower bound on the mass of N₁ and the upper bound on the reheating temperature of the Universe after inflation. A modest resolution of this conundrum is proposed.