Quark Matter Viscosity

A lot of interest in the study of viscosity of quark matter has been stimulated in the recent years by the experiments carried out at the relativistic heavy-ion collider (RHIC), which seem to indicate that above the critical temperature the quark-gluon plasma (QGP) formed in these experiments behaves as a fluid – a ‘strongly-coupled matter’, with quite a small viscosity (i.e. almost a perfect liquid). This conclusion is mostly based on the fact that QGP formed in RHIC was well described by an ideal hydrodynamics model, and the findings on the v2 coefficient measured in the multipole analysis of the angular distribution of the hadrons produced in the ultrarelativistic collisions suggesting substantial collective flow (“elliptic” flow) to imply that the viscosity cannot be very large. Thus, transport properties of quark mater are of great interest both experimentally and theoretically. It is also known that viscosity of nuclear matter plays an important role in the damping of neutron star oscillations and instabilities. Information about quark matter viscosity is essential in understanding damping of non-radial modes of oscillations in hybrid stars that is neutron stars with quark matter in the core. In this note, we present preliminary results of the calculations of quark matter viscosity in the framework of Nambu Jonalasinio model.