Amplified Fermion Production from Overpopulated Bose Fields

TL;DR

This paper investigates how highly occupied bosonic fields can dramatically amplify fermion production in a linear sigma model, revealing rapid thermalization of fermions even when bosons are far from equilibrium.

Contribution

It demonstrates the significant enhancement of fermion production due to overpopulated bosonic fields and compares multiple methods to analyze this phenomenon.

Findings

Fermion production is dramatically amplified by highly occupied bosonic quanta.

Strongly coupled fermions rapidly approach a Fermi-Dirac distribution with evolving parameters.

Bosons remain far from equilibrium during the fermion thermalization process.

Abstract

We study the real-time dynamics of fermions coupled to scalar fields in a linear sigma model, which is often employed in the context of preheating after inflation or as a low-energy effective model for quantum chromodynamics. We find a dramatic amplification of fermion production in the presence of highly occupied bosonic quanta for weak as well as strong couplings. For this we consider the range of validity of different methods: lattice simulations with male/female fermions, the mode functions approach and the quantum 2PI effective action with its associated kinetic theory. For strongly coupled fermions we find a rapid approach to a Fermi-Dirac distribution with time-dependent temperature and chemical potential parameters, while the bosons are still far from equilibrium.