Thermal leptogenesis in a model with mass varying neutrinos

In this paper we consider the possibility of the neutrino mass varying during the evolution of the Universe and study its implications on leptogenesis. Specifically, we take the minimal seesaw model of neutrino masses and introduce a coupling between the right-handed neutrinos and the dark energy scalar field, the quintessence. In our model, the right-handed neutrino masses change as the quintessence evolves. We then examine in detail the parameter space of this model allowed by the observed baryon number asymmetry. Our results show that it is possible to lower the reheating temperature in this scenario in comparison with the case that the neutrino masses are unchanged, which helps solve the gravitino problem. Furthermore, a degenerate neutrino mass pattern with $m_i$ larger than the upper limit given in the minimal leptogenesis scenario is permitted.