We construct a model to describe dense hadronic matter at zero and finite temperatures, based on the parity doublet model of DeTar and Kunihiro [C. E. DeTar and T. Kunihiro, Phys. Rev. D 39, 2805 (1989)], including the isosinglet scalar meson $\sigma$ as well as $\rho$ and $\omega$ mesons. We show that, by including a six-point interaction of the $\sigma$ meson, the model reasonably reproduces the properties of normal nuclear matter with the chiral invariant nucleon mass $m_0$ in the range from 500 to 900 MeV. Furthermore, we study the phase diagram based on the model, which shows that the value of the chiral condensate drops at the liquid-gas phase transition point and at the chiral phase transition point. We also study asymmetric nuclear matter and find that the first-order phase transition for the liquid-gas phase transition disappears in asymmetric matter and that the critical density for the chiral phase transition at nonzero density becomes smaller for larger asymmetry.

• Received 11 May 2015

DOI:https://doi.org/10.1103/PhysRevC.92.025201