Shear viscosity and phase diagram from Polyakov–Nambu–Jona-Lasinio model

We present a detailed study of the variation of shear viscosity η, with temperature and baryon chemical potential within the framework of the Polyakov--Nambu--Jona-Lasinio model. η is found to depend strongly on the spectral width of the quasiparticles present in the model. The variation of η across the phase diagram has distinctive features for different kinds of transitions. These variations have been used to study the possible location of the critical end point and are cross-checked with similar studies of variations of specific heat. Finally, using a parametrization of the freeze-out surface in heavy-ion collision experiments, the variation of the shear viscosity to entropy density ratio has also been discussed as a function of the center-of-mass energy of collisions.