Diquark Bose Condensates in High Density Matter and Instantons

Abstract

Instantons lead to strong correlations between up and down quarks with spin zero and anti-symmetric color wave functions. In cold and dense matter, \(n_b>n_c\simeq 1 fm^{-3}\) and \(T<T_c\sim\) 50 MeV, these pairs Bose-condense, replacing the usual \(< \bar qq >\) condensate and restoring chiral symmetry. At high density, the ground state is a color superconductor in which diquarks play the role of Cooper pairs. An interesting toy model is provided by QCD with two colors: it has a particle-anti-particle symmetry which relates \(<\bar qq>\) and \(< qq>\) condensates.