Nonlocal Polyakov–Nambu–Jona-Lasinio model and imaginary chemical potential

With the aim of setting constraints for the modeling of the QCD phase diagram, the phase structure of the two-flavor Polyakov-loop-extended Nambu and Jona-Lasinio (PNJL) model is investigated in the range of imaginary chemical potentials (μI) and compared with available Nf=2 lattice QCD results. The calculations are performed using the advanced nonlocal version of the PNJL model with the inclusion of vector-type quasiparticle interactions between quarks, and with wave-function-renormalization corrections. It is demonstrated that the nonlocal PNJL model reproduces important features of QCD at finite μI, such as the Roberge-Weiss (RW) periodicity and the RW transition. Chiral and deconfinement transition temperatures for Nf=2 turn out to coincide both at zero chemical potential and at finite μI. Detailed studies are performed concerning the RW endpoint and its neighborhood where a first-order transition occurs.