Flavored Quantum Boltzmann Equations

TL;DR

This paper derives quantum Boltzmann equations from first principles to model flavor oscillations, collisions, and time-dependent mass effects in the early universe, providing insights into baryogenesis mechanisms.

Contribution

It introduces a first-principles derivation of quantum Boltzmann equations for flavor dynamics with a time-dependent mass matrix, applied to a toy model of baryogenesis.

Findings

CP asymmetry arises from coherent flavor oscillations.

Collisions influence flavor evolution in different regimes.

Numerical solutions reveal the interplay of oscillations and interactions.

Abstract

We derive from first principles, using non-equilibrium field theory, the quantum Boltzmann equations that describe the dynamics of flavor oscillations, collisions, and a time-dependent mass matrix in the early universe. Working to leading non-trivial order in ratios of relevant time scales, we study in detail a toy model for weak scale baryogenesis: two scalar species that mix through a slowly varying time-dependent and CP-violating mass matrix, and interact with a thermal bath. This model clearly illustrates how the CP asymmetry arises through coherent flavor oscillations in a non-trivial background. We solve the Boltzmann equations numerically for the density matrices, investigating the impact of collisions in various regimes.