Nonequilibrium chiral perturbation theory and disoriented chiral condensates

TL;DR

This paper extends Chiral Perturbation Theory to non-equilibrium meson gases using a time-dependent pion decay constant and Schwinger-Keldysh formalism, exploring Disoriented Chiral Condensate formation in heavy-ion collisions.

Contribution

It introduces a non-equilibrium extension of Chiral Perturbation Theory with a novel renormalization approach and applies it to DCC formation via parametric resonance.

Findings

Successful renormalization with two new low-energy constants

Demonstration of DCC domain formation in the model

Application to heavy-ion collision scenarios

Abstract

We analyse the extension of Chiral Perturbation Theory to describe a meson gas out of thermal equilibrium. For that purpose, we let the pion decay constant be a time-dependent function and work within the Schwinger-Keldysh contour technique. A useful connection with curved space-time QFT allows to consistently renormalise the model, introducing two new low-energy constants in the chiral limit. We discuss the applicability of our approach within a Relativistic Heavy-Ion Collision environment. In particular, we investigate the formation of Disoriented Chiral Condensate domains in this model, via the parametric resonance mechanism.