Chiral Symmetry Restoration in the Instanton Liquid at Finite Density

Abstract

The properties of the QCD partition function at finite chemical potential are studied within the instanton liquid model. It is shown that the density dependence of the quark-induced instanton-antiinstanton (I-A) interaction leads to the formation of topologically neutral I-A pairs ('molecules'), resulting in a first order chiral phase transition at a critical chemical potential $\mu_q^c\simeq 310$ MeV. At somewhat higher densities ($\mu_q\ge360$ MeV), the quark Fermi surface becomes instable with respect to diquark condensation (Cooper pairs) generating BCS-type energy gaps of order 50 MeV.