Gravitational neutrino reheating

Despite having important cosmological implications, the reheating phase is believed to play a crucial role in cosmology and particle physics model building. Conventionally, the model of reheating with an arbitrary coupling of inflaton to massless fields naturally lacks precise prediction and hence difficult to verify through observation. In this paper, we propose a simple and natural reheating mechanism where the particle physics model, namely the Type-I seesaw is shown to play a major role in the entire reheating process where inflaton is coupled with all the fields only gravitationally. Besides successfully resolving the well-known neutrino mass and baryon asymmetry problems, this scenario offers successful reheating, predicts distinct primordial gravitational wave spectrum and non-vanishing lowest active neutrino mass. Our novel mechanism opens up a new avenue of integrating particle physics and cosmology in the context of reheating.