Wash-In Leptogenesis
  We present a leptogenesis mechanism based on the standard type-I seesaw model
that successfully operates at right-handed-neutrino masses as low as a few 100
TeV. This mechanism, which we dub "wash-in leptogenesis", does not require any
CP violation in the neutrino sector and can be implemented even in the regime
of strong wash-out. The key idea behind wash-in leptogenesis is to generalize
standard freeze-out leptogenesis to a nonminimal cosmological background in
which the chemical potentials of all particles not in chemical equilibrium at
the temperature of leptogenesis are allowed to take arbitrary values. This sets
the stage for building a plethora of new baryogenesis models where chemical
potentials generated at high temperatures are reprocessed to generate a
nonvanishing B-L asymmetry at low temperatures. As concrete examples, we
discuss wash-in leptogenesis after axion inflation and in the context of grand
unification.
