Effective Theory of Superfluid Quark Matter

We provide a brief introduction to the high density effective theory of QCD. As an application, we consider the instanton correction to the perturbatively generated gap in the color superconducting phase. We show that the instanton correction becomes large for μ ~ 1.25 GeV in N_f = 2 QCD, and for μ ~ 750 MeV in N_f = 3 QCD with a massive strange quark. We also study some other numerical issues related to the magnitude of the gap. We find, in particular, that a renormalization group improved gap equation does not give results that are substantially different from a gap equation with a fixed coupling.