Coherent quantum Boltzmann equations from cQPA

TL;DR

This paper develops a refined quantum kinetic theory using the coherent quasiparticle approximation, enabling self-consistent quantum Boltzmann equations that incorporate nonlocal coherence effects for fermions and scalars, with applications to baryogenesis.

Contribution

The authors extend their quantum kinetic framework by deriving explicit propagators and resummed collision integrals that include coherence, leading to new self-consistent Boltzmann equations for interacting fields.

Findings

Derived explicit cQPA propagators in homogeneous backgrounds.

Resummed collision integrals to all orders in gradient expansion.

Applied the formalism to a toy model of coherent baryogenesis.

Abstract

We reformulate and extend our recently introduced quantum kinetic theory for interacting fermion and scalar fields. Our formalism is based on the coherent quasiparticle approximation (cQPA) where nonlocal coherence information is encoded in new spectral solutions at off-shell momenta. We derive explicit forms for the cQPA propagators in the homogeneous background and show that the collision integrals involving the new coherence propagators need to be resummed to all orders in gradient expansion. We perform this resummation and derive generalized momentum space Feynman rules including coherent propagators and modified vertex rules for a Yukawa interaction. As a result we are able to set up self-consistent quantum Boltzmann equations for both fermion and scalar fields. We present several examples of diagrammatic calculations and numerical applications including a simple toy model for coherent baryogenesis.