A semi-variational approach to QCD at finite temperature and baryon density

TL;DR

This paper introduces a semi-variational method to derive an effective action for QCD at finite temperature and baryon density, incorporating excited states and non-zero baryon number, tested on a four-fermion model.

Contribution

It extends a bosonization-based variational approach to include finite density and temperature effects in QCD, accounting for excited states and baryon number.

Findings

Derived an effective action for QCD at finite temperature and density.

Validated the approach using a four-fermion interaction model.

Demonstrated the method's ability to handle excited states and baryon number.

Abstract

Recently a new bosonization method has been used to derive, at zero fermion density, an effective action for relativistic field theories whose partition function is dominated by fermionic composites, chiral mesons in the case of QCD. This approach shares two important features with variational methods: the restriction to the subspace of the composites, and the determination of their structure functions by a variational calculation. But unlike standard variational methods it treats excited states at the same time and on the same footing as the ground state. I extend this method including states of nonvanishing fermion (baryon) number and derive an effective action for QCD at finite temperature and baryon density. I test the result on a four-fermion interaction model.