Speaker
Description
In this talk, I will discuss the generation of a lepton asymmetry during
a first-order cosmological phase transition at which the sterile neutrinos of the seesaw
mechanism acquire their masses. Contrary to previous works who studied the same
problem, we compute the lepton asymmetry by solving quantum kinetic equations
derived from nonequilibrium quantum field theory, which take into account the time
variation of the sterile neutrino masses and the subsequent particle creation.
We consider two scenarios: (i) the so-called mass gain mechanism, in which the origin
of the asymmetry is the decays of the sterile neutrinos brought strongly out of equilibrium
by the phase transition; (ii) the ARS mechanism, in which the asymmetry is produced
by the oscillations of GeV-scale sterile neutrinos. In both cases, we identify the region
of parameter space leading to successful leptogenesis.
