Quintessential Kination and Leptogenesis

We show how thermal leptogenesis induced by the CP-violating decay of a right-handed neutrino (RHN) can be compatible to the assumption of quintessential kination, i.e., to a cosmological background model where the energy density of the early Universe is assumed to be dominated by the kinetic term of a quintessence field during some epoch of its evolution. The phenomenology depends on the temperature T(r) above which kination dominates over radiation. For instance, when kination stops to dominate when M/100 less than or similar to T(r) less than or similar to M (where M is the RHN mass) the efficiency of the process eta, defined as the ratio between the produced lepton asymmetry and the amount of CP violation in the RHN decay, can be even larger than in the standard scenario of radiation domination. On the other hand, a super-weak wash-out regime is obtained (eta << 1) for T(r) << M/100. In this latter situation the lower bound T(r) greater than or similar to 5 MeV x (M/TeV) (0.05 eV/(m) over tilde) can be found, where (m) over tilde is the effective neutrino mass scale.