Chiral phase transition at high temperature and density in the QCD-like theory

Abstract

The chiral phase transition at finite temperature T and/or chemical potential $\mu$ is studied using the QCD-like theory with a variational approach. The ``QCD-like theory'' means the improved ladder approximation with an infrared cutoff in terms of a modified running coupling. The form of Cornwall-Jackiw-Tomboulis effective potential is modified by the use of the Schwinger-Dyson equation for generally nonzero current quark mass. We then calculate the effective potential at finite T and/or $\mu$ and investigate the phase structure in the chiral limit. We have a second-order phase transition at $T_c=129$ MeV for $\mu =0$ and a first-order one at ${\mu }_c=422$ MeV for T=0. A tricritical point in the T-$\mu$ plane is found at T=107 MeV, $\mu =210$ MeV. The position is close to that of the random matrix model and some version of the Nambu-Jona-Lasinio model.

Comments: 10 pages, 6 figures. Accepted for publication in Physical Review D