Phase diagram in the imaginary chemical potential region and extended Z3 symmetry

TL;DR

This paper investigates phase transitions in the imaginary chemical potential region using an extended Z3 symmetric PNJL model, revealing various transition types and the effects of eight-quark interactions.

Contribution

It introduces an extended Z3 invariant PNJL model with eight-quark interactions to study phase transitions and RW periodicity in the imaginary chemical potential region.

Findings

Identifies four types of phase transitions: deconfinement, chiral, Polyakov-loop RW, and chiral RW.

Shows the order of chiral and deconfinement transitions depends on quark mass.

Finds eight-quark interactions shift the chiral transition near the deconfinement transition.

Abstract

Phase transitions in the imaginary chemical potential region are studied by the Polyakov loop extended Nambu-Jona-Lasinio (PNJL) model that possesses the extended Z3 symmetry. The extended Z3 invariant quantities such as the partition function, the chiral condensate and the modifed Polyakov loop have the Roberge-Weiss (RW) periodicity. There appear four types of phase transitions; deconfinement, chiral, Polykov-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 Polykov-loop RW and chiral RW transitions do not. The scalar-type eightquark interaction newly added in the model makes the chiral transition line shift to the vicinity of the deconfiment transition line.