Thermal leptogenesis with triplet Higgs boson and mass varying neutrinos

We study the thermal leptogenesis in the scenario where the standard model is extended to include one $\mathrm{S}\mathrm{U}(2{)}_L$ triplet Higgs boson, in addition to three generations of the right-handed neutrinos. In the model, we introduce the coupling between the quintessence and the right-handed neutrinos, the triplet Higgs boson, so that the light neutrino masses vary during the evolution of the Universe. Assuming that the lepton number asymmetry is generated by the decays of the lightest right-handed neutrino $N_1$, we find the thermal leptogenesis can be characterized by four model independent parameters. In the case where the contribution of the triplet Higgs to the lepton asymmetry is dominant, we give the relation between the minimal $M_1$ and the absolute mass scale $\overline{m}$ of the light neutrinos, by solving the Boltzmann equations numerically. We will also show that, with the varying neutrino masses, the reheating temperature can be lowered in comparison to the traditional thermal leptogenesis.