Instability-induced fermion production in quantum field theory

TL;DR

This paper demonstrates that nonequilibrium instabilities in quantum field theory can lead to rapid fermion production via boson amplification, with dynamics captured by a 1/N expansion of the 2PI effective action.

Contribution

It introduces a novel analysis of fermion production driven by boson instabilities using a 1/N expansion including boson-fermion loops.

Findings

Fermion production is highly efficient during boson amplification.

Fermion occupation reaches thermal levels in the infrared.

High-momentum fermion modes follow a power-law decay with exponent two.

Abstract

Nonequilibrium instabilities are known to lead to exponential amplification of boson occupation numbers for low momentum modes on time scales much shorter than the asymptotic thermal equilibration time. We show for Yukawa-type interactions that this growth induces very efficient fermion production, which proceeds with the maximum primary boson growth rate. The description is based on a 1/N expansion of the 2PI effective action to NLO including boson-fermion loops, which are crucial to observe this phenomenon. For long enough amplification in the boson sector, fermion production terminates when the thermal occupancy is reached in the infrared. At higher momenta, where boson occupation numbers are low, the fermion modes exhibit a power-law regime with exponent two.