Quantum Boltzmann equations and leptogenesis

Abstract

The closed time-path formalism is a powerful Green’s function formulation to describenon-equilibrium phenomena in field theory and it leads to a complete non-equilibriumquantum kinetic theory. We make use of this formalism to write down the set of quantumBoltzmann equations relevant for leptogenesis. They manifest memory effects andoff-shell corrections. In particular, memory effects lead to a time-dependent CPasymmetry whose value at a given instant of time depends upon the previoushistory of the system. This result is particularly relevant when the asymmetry isgenerated by the decays of nearly mass-degenerate heavy states, as in resonant or softleptogenesis.