Bulk Viscosity in 2SC Quark Matter
Washington Univ., St. Louis
Quark matter inside a compact star is most likely a color superconductor. Many suggestions have been made for possible color-superconducting phases, from more or less conventional BCS superconductors to more exotic ones, breaking rotational or translational invariance and exhibiting gapless modes. One approach to determine the ground state among this multitude of possibilities is to compute their transport properties and compare the resulting predictions with astrophysical observations. I will discuss one of these transport properties, namely bulk viscosity of three-flavor color-superconducting quark matter in the 2SC phase. Bulk viscosity is necessary to damp "r-modes" in a compact star which otherwise (=assuming a perfect fluid) would grow unstable and lead to rotational frequencies of the star which are incompatible with observations.