Leptogenesis in an inflationary universe

We investigate leptogenesis via decays of heavy Majorana neutrinos which are produced nonthermally in inflaton decays. We make a comprehensive study on leptogenesis assuming various supersymmetric (SUSY) models for hybrid, new, and topological inflations. For an estimation of the lepton asymmetry we adopt the Froggatt-Nielsen mechanism for mass matrices of quarks and leptons. We find that all of these models are successful in producing enough lepton asymmetry to explain the baryon number in the present universe. Here we impose low reheating temperatures such as TR10⁸GeV in order to suppress the abundance of gravitinos so they do not conflict with big-bang nucleosynthesis. Furthermore, we find that leptogenesis works very well even with TR10⁶GeV in the SUSY hybrid or new inflation model. It is known that such a reheating temperature is low enough to suppress the abundance of gravitinos of mass m3/2100GeV--1 TeV. Thus, leptogenesis is fully consistent with big-bang nucleosynthesis in a wide region of the gravitino mass.