Remarks on the chiral phase transition in chromodynamics

Abstract

The phase transition restoring chiral symmetry at finite temperatures is considered in a linear $\sigma$ model. For three or more massless flavors, the perturbative $\epsilon$ expansion predicts the phase transition is of first order. At high temperatures, the ${\mathrm{U}}_A\mathrm{}\left(1\right)\mathrm{}$ symmetry will also be effectively restored.