Abstract
We study leptogenesis from the out-of-equilibrium decays of the
lightest heavy neutrino N1 in the medium (low) temperature
regime, T≲1012 GeV (109 GeV), where the rates of
processes mediated by the τ (and μ) Yukawa coupling are non
negligible, implying that the effects of lepton flavors must be
taken into account. We find important quantitative and qualitative
differences with respect to the case where flavor effects are
ignored: (i) The cosmic baryon asymmetry can be enhanced by up to
one order of magnitude; (ii) The sign of the asymmetry can be
opposite to what one would predict from the sign of the total lepton
asymmetry 
1; (iii) Successful leptogenesis is possible
even with 1 = 0.
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