Hiroaki Kouno

Polyakov loop extended Nambu-Jona-Lasinio model with imaginary chemical potential

The Polyakov loop extended Nambu--Jona-Lasinio (PNJL) model with imaginary chemical potential is studied. The model possesses the extended

Entanglement between deconfinement transition and chiral symmetry restoration

{\mathbb{Z}}_{3}

Phase diagram in the imaginary chemical potential region and extended Z{sub 3} symmetry

symmetry that QCD does. Quantities invariant under the extended

Critical endpoint in the Polyakov-loop extended NJL model

{\mathbb{Z}}_{3}

Chiral phase transition in an extended NJL model with higher-order multi-quark interactions

symmetry, such as the partition function, the chiral condensate, and the modified Polyakov loop, have Roberge-Weiss periodicity. The phase diagram of confinement/deconfinement transition derived with the PNJL model is consistent with the Roberge-Weiss prediction on it and the results of lattice QCD. The phase diagram of chiral transition is also presented by the PNJL model.

Determination of QCD phase diagram from the imaginary chemical potential region

We extend the Polyakov-loop extended Nambu-Jona-Lasinio model by introducing an effective four-quark vertex depending on the Polyakov loop. The effective vertex generates entanglement interactions between the Polyakov loop and the chiral condensate. The new model is consistent with lattice QCD data at imaginary quark-number chemical potential and real and imaginary isospin chemical potentials, particularly on the strong correlation between the chiral and deconfinement transitions and also on the quark-mass dependence of the order of the Roberge-Weiss endpoint. We investigate the influence of the entanglement interactions on the location of the tricritical point at real isospin chemical potential and on the location of the critical endpoint at real quark-number chemical potential.

Vector-type four-quark interaction and its impact on QCD phase structure

Phase transitions in the imaginary chemical potential region are studied by the Polyakov-loop extended Nambu-Jona-Lasinio model that possesses the extended Z{sub 3} symmetry. The extended-Z{sub 3} invariant quantities such as the partition function, the chiral condensate, and the modified Polyakov loop have the Roberge-Weiss (RW) periodicity. There appear four types of phase transitions: deconfinement, chiral, Polyakov-loop RW, and chiral RW transitions. The orders of the chiral and deconfinement transitions depend on the presence or absence of current quark mass, but those of the Polyakov-loop RW and chiral RW transitions do not. The scalar-type, eight-quark interaction newly added in the model makes the chiral transition line shift to the vicinity of the deconfinement transition line.

The Roberge?Weiss phase transition and its endpoint

Abstract 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 ( σ 4 ) interaction and the vector type four-quark interaction are newly added. The σ 4 interaction largely shifts the CEP toward higher temperature and lower chemical potential, while the vector type interaction does oppositely. At zero chemical potential, the σ 4 interaction moves the pseudo-critical temperature of the chiral phase transition to the vicinity of that of the deconfinement phase transition.

Confinement and

Abstract The chiral phase transition is studied in an extended Nambu–Jona-Lasinio model with eight-quark interactions. Equations for scalar and vector quark densities, derived in the mean field approximation, are nonlinear and mutually coupled. The scalar type nonlinear term hastens the restoration of chiral symmetry, while the scalar–vector mixing term makes the transition sharper. The scalar type nonlinear term shifts the critical endpoint toward the values predicted by lattice QCD simulations and the QCD-like theory.

\mathbb {Z}_{3}

We test the reliability of the Polyakov-loop extended Nambu-Jona-Lasinio (PNJL) model, comparing the model result with the lattice data at nonzero imaginary chemical potential. The PNJL model with the vector-type four-quark and scalar-type eight-quark interactions reproduces the lattice data on the pseudocritical temperatures of the deconfinement and chiral phase transitions. The QCD phase diagram in the real chemical potential region is predicted by the PNJL model. The critical end point survives, even if the vector-type four-quark interaction is taken into account.