High density quark matter and the renormalization group in QCD with two and three flavors

We consider the most general four fermion operators in QCD for two and thre e massless flavors and study their renormalization in the vicinity of the F ermi surface. We show that, asymptotically, the largest coupling correspond s to scalar diquark condensation. Asymptotically the direct and iterated (m olecular) instanton interactions become equal. We provide simple arguments for the form of the operators that diagonalize the evolution equations. Som e solutions of the flow equations exhibit instabilities arising out of pure ly repulsive interactions. (C) 1999 Elsevier Science B.V. All rights reserv ed.