Kinetic theory for scalar fields with nonlocal quantum coherence

TL;DR

This paper develops quantum kinetic equations for scalar fields, revealing new spectral solutions that describe coherent evolution and particle production, with applications to the Klein problem and unstable fields.

Contribution

It introduces a spectral phase space framework for quantum coherence in scalar fields, enabling consistent descriptions of coherent evolution with collisions.

Findings

New spectral solutions for the 2-point correlation function

Application to the Klein problem and bound states

Comparison of particle number definitions in nonequilibrium theory

Abstract

We derive quantum kinetic equations for scalar fields undergoing coherent evolution either in time (coherent particle production) or in space (quantum reflection). Our central finding is that in systems with certain space-time symmetries, quantum coherence manifests itself in the form of new spectral solutions for the dynamical 2-point correlation function. This spectral structure leads to a consistent approximation for dynamical equations that describe coherent evolution in presence of decohering collisions. We illustrate the method by solving the bosonic Klein problem and the bound states for the nonrelativistic square well potential. We then compare our spectral phase space definition of particle number to other definitions in the nonequilibrium field theory. Finally we will explicitly compute the effects of interactions to coherent particle production in the case of an unstable field coupled to an oscillating background.