Leptogenesis from an (N)over-tilde-dominated early universe -: art. no. 043512

We investigate in detail leptogenesis by the decay of a coherent right-handed sneutrino (N) over tilde having dominated the energy density of the early universe, which was originally proposed by two of the authors (H.M. and T.Y.). Once the (N) over tilde dominant universe is realized, the amount of generated lepton asymmetry (and hence baryon asymmetry) is determined only by the properties of the right-handed neutrino, regardless of the history before it dominates the universe. Moreover, thanks to the entropy production by the decay of the right-handed sneutrino, thermally produced relies are sufficiently diluted, In particular, the cosmological gravitino problem can be avoided even when the reheating temperature of inflation is higher than 10(10) GeV, in a wide range of the gravitino mass m(3/2)similar or equal to10 MeV-100TeV. If the gravitino mass is in the range m(3/2)similar or equal to10 MeV-1 GeV as in some gauge-mediated super-symmetry breaking models, the dark matter in our Universe can be dominantly composed of the gravitino. The quantum fluctuation of N during inflation causes an isocurvature fluctuation which may be detectable in the future.