Critical endpoint in the Polyakov-loop extended NJL model

The critical endpoint (CEP) and the phase structure are studied in the Polyakov-loop extended Nambu-Jona-Lasinio model in which the scalar type eight-quark (σ4) interaction and the vector type four-quark interaction are newly added. The σ4 interaction largely shifts the CEP toward higher temperature and lower chemical potential, while the vector type interaction does oppositely. At zero chemical potential, the σ4 interaction moves the pseudo-critical temperature of the chiral phase transition to the vicinity of that of the deconfinement phase transition.