Some aspects of thermal leptogenesis

Properties of neutrinos may be the origin of the matter-antimatter asymmetryof the universe. In the seesaw model for neutrino masses this leads toimportant constraints on the properties of light and heavy neutrinos. Inparticular, an upper bound on the light neutrino masses of 0.1 eV can bederived. We review the present status of thermal leptogenesis with emphasis onthe theoretical uncertainties and discuss some implications for lepton andquark mass hierarchies, CP violation and dark matter. We also comment on the`leptogenesis conspiracy', the remarkable fact that neutrino masses may lie inthe range where leptogenesis works best.Comment: 23 pages, 5 figures, submitted to the Focus on Neutrino Physics issue of the New Journal of Physics, edited by F. Halzen, M. Lindner and A. Suzuk