Quantum Leptogenesis I

TL;DR

This paper presents a quantum mechanical approach to leptogenesis using Kadanoff-Baym equations, revealing that damping effects and rapid oscillations significantly influence the predicted matter-antimatter asymmetry.

Contribution

It introduces a full quantum calculation of leptogenesis that accounts for memory effects and oscillations, refining previous Boltzmann-based models.

Findings

Memory effects and oscillations suppress lepton asymmetry

Thermal damping from gauge interactions offsets quantum enhancements

Boltzmann equations remain accurate despite quantum corrections

Abstract

Thermal leptogenesis explains the observed matter-antimatter asymmetry of the universe in terms of neutrino masses, consistent with neutrino oscillation experiments. We present a full quantum mechanical calculation of the generated lepton asymmetry based on Kadanoff-Baym equations. Origin of the asymmetry is the departure from equilibrium of the statistical propagator of the heavy Majorana neutrino, together with CP violating couplings. The lepton asymmetry is calculated directly in terms of Green's functions without referring to "number densities". Compared to Boltzmann and quantum Boltzmann equations, the crucial difference are memory effects, rapid oscillations much faster than the heavy neutrino equilibration time. These oscillations strongly suppress the generated lepton asymmetry, unless the standard model gauge interactions, which cause thermal damping, are properly taken into account. We find that these damping effects essentially compensate the enhancement due to quantum statistical factors, so that finally the conventional Boltzmann equations again provide rather accurate predictions for the lepton asymmetry.