On Higgs and sphaleron effects during the leptogenesis era

We discuss the effects of various processes that can be active during theleptogenesis era, and present the Boltzmann equations that take them intoaccount appropriately. A non-vanishing Higgs number asymmetry is alwayspresent, enhancing the washout of the lepton asymmetry. This is the main neweffect when leptogenesis takes place at $T>10^{12}$ GeV, reducing the finalbaryon asymmetry and tightening the leptogenesis bound on the neutrino masses.If leptogenesis occurs at lower temperatures, electroweak sphalerons partiallytransfer the lepton asymmetry to a baryonic one, while Yukawa interactions andQCD sphalerons partially transfer the asymmetries of the left-handed fields tothe right-handed ones, suppressing the washout processes. Depending on thespecific temperature range in which leptogenesis occurs, the final baryonasymmetry can be enhanced or suppressed by factors of order 20%--40% withrespect to the case when these effects are altogether ignored.Comment: one reference adde