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

Understand

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.