EOS and Bulk Viscosity of Cold Quark Matter in a Running Coupling NJL Model

We analyze the thermodynamical properties of color superconducting quark matter in the isotropic color spin locking (iso-CSL) phase at zero temperature and finite chemical potential. We perform calculations in the NJL model with quark-quark and quark-antiquark coupling for two parametrizations of the coupling strength: (a) constant value and (b) logarithmic dependence on the chemical potential. The bulk viscosity of the iso-CSL phase is calculated for both parametrizations for electrically neutral two-flavor matter in -equilibrium. We discuss an extension of this model to the three-flavor case where we find that behaviour of the strange quark mass is qualitatively different for the cases (a) and (b). In this context we examine the influence of the value of QCD momentum scale QCD and investigate the stability of three-flavor quark matter in the iso-CSL phase under compact star (CS) constraints. (authors)