Nonperturbative production of fermions and the baryon asymmetry

One simple possibility for generating the present baryon asymmetry is leptogenesis. It only requires the presence of right handed neutrinos (which naturally arise in many extensions of the Standard Model) and depends crucially on the mechanism responsible for their production. In particular, when their mass exceeds the inflaton mass (10^13 GeV in chaotic inflation) only non perturbative production can occur. It is reported here that non perturbative production of fermions in an expanding Universe is a very efficient mechanism up to masses of order of (10^17 – 10^18) GeV, and that it can be easily applied to solve the baryon asymmetry problem.