  In two recent papers, arXiv:0909.1559 and arXiv:0911.4122, it has been
demonstrated that one can obtain quantum corrected Boltzmann kinetic equations
for leptogenesis using a top-down approach based on the
Schwinger-Keldysh/Kadanoff-Baym formalism. These "Boltzmann-like" equations are
similar to the ones obtained in the conventional bottom-up approach but differ
in important details. In particular there is a discrepancy between the
CP-violating parameter obtained in the first-principle derivation and in the
framework of thermal field theory. Here we demonstrate that the two approaches
can be reconciled if causal n-point functions are used in the thermal field
theory approach. The new result for the medium correction to the CP-violating
parameter is qualitatively different from the conventional one. The analogy to
a toy model considered earlier enables us to write down consistent quantum
corrected Boltzmann equations for thermal leptogenesis in the Standard Model
(supplemented by three right-handed neutrinos) which include quantum
statistical terms and medium corrected expressions for the CP-violating
parameter.
