The (2+1)-dimensional NJL model at finite temperature

We decribe properties of (2+1)-dimensional Nambu–Jona-Lasinio (NJL) models at finite temperature, beginning with the model with a discrete chiral symmetry. We then consider the model with a continuous U(1)×U(1) chiral symmetry, describing the restoration of the symmetry at finite temperature. In each case, we compute the free energy and comment on a recently proposed constraint based upon it. We conclude with a brief discussion of NJL models with larger chiral symmetries.