Kinetic theory for particle production

TL;DR

This paper examines the compatibility of effective viscous pressure models with kinetic theory in cosmological particle production, finding consistency in homogeneous but not in inhomogeneous spacetimes.

Contribution

It provides a comparison between phenomenological viscous pressure models and kinetic theory in the context of cosmological particle production.

Findings

Effective viscous pressure models are consistent with kinetic theory in homogeneous spacetimes.

Inhomogeneous spacetimes show inconsistency with the viscous pressure approach.

The study clarifies the applicability limits of viscous pressure models in cosmology.

Abstract

Recently, the phenomenological description of cosmological particle production processes in terms of effective viscous pressures has attracted some attention. Using a simple creation rate model we discuss the question to what extent this approach is compatible with the kinetic theory of a relativistic gas. We find the effective viscous pressure approach to be consistent with this model for homogeneous spacetimes but not for inhomogeneous ones.