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 (\(\mu_\mathrm{I}\)) and compared with available \(N_f=2\) 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 \(\mu_\mathrm{I}\), such as the Roberge-Weiss (RW) periodicity and the RW transition. Chiral and deconfinement transition temperatures for \(N_f=2\) turn out to coincide both at zero chemical potential and at finite \(\mu_\mathrm{I}\). Detailed studies are performed concerning the RW endpoint and its neighborhood where a first-order transition occurs.