  In this talk, I present a novel and minimal alternative to thermal
leptogenesis, which builds upon the assumption that the electroweak gauge
bosons are coupled to an axion-like scalar field, as it is, for instance, the
case in certain string compactifications. The motion of this axion-like field
after the end of inflation generates an effective chemical potential for
leptons and antileptons, which, in the presence of lepton number-violating
scatterings mediated by heavy Majorana neutrinos, provides an opportunity for
baryogenesis via leptogenesis. In contrast to thermal leptogenesis, the final
baryon asymmetry turns out to be insensitive to the masses and CP-violating
phases in the heavy neutrino sector. Moreover, the proposed scenario requires a
reheating temperature of at least O(10^12) GeV and it is, in particular,
consistent with heavy neutrino masses close the scale of grand unification.
This talk was given in February 2015 at HPNP 2015 at Toyama University and is
based on recent work (arXiv:1412.2043 [hep-ph]) in collaboration with A.
Kusenko and T. T. Yanagida.
