What Happens When You Squeeze a Neutron Star?

It has been known for some time that the ground state of matter at asymptotically high densities is a color superconductor. There has been a lot of effort to understand the many different phases of high density QCD, specifically trying to come up with possible observations that might distinguish them. The only possible place to study these high density phases would be in the core of compact (neutron) stars. I will discuss this problem in general and then focus on one transport property in particular: the bulk viscosity. A large bulk viscosity is desired to damp out the "r-mode instabilities" that naturally arise in a rotating compact star. I will sketch out the general calculation of the bulk viscosity and show some results specific to the warm CFL phase with kaons.