Phase diagram and bulk thermodynamical quantities in the Nambu–Jona-Lasinio model at finite temperature and density

We reexamine the recent instanton motivated studies of Alford, Rajagopal, and Wilczek, and Berges and Rajagopal in the framework of the standard SU(2) Nambu--Jona-Lasinio (NJL) model. The chiral phase diagram is calculated in the temperature-density plane, and the pressure is evaluated as the function of the quark density. Obtaining simple approximate relations describing the T-{μ} and T-pF phase transition lines, we find that the results of the instanton based model and that of the NJL model are identical. The diquark transition line is also given.