Bulk viscosity of strange quark matter in a density-dependent quark mass model and dissipation of the r mode in strange stars

We study the bulk viscosity of the strange quark matter in the density-dependent quark mass model (DDQM) under the background of self-consistent thermodynamics. The correct formula of the viscosity is derived. We also find that the viscosity in the DDQM is larger by two to three orders of magnitude than that in MIT bag model. We calculate the damping time scale due to the coupling of the viscosity and r mode. The numerical results show that the time scale cannot be shorter than 10{sup -1} s.