Diquark condensation and the quark-quark interaction - art. no. 065208

We employ a bispinor gap equation to study superfluidity at nonzero chemica l potential, mu not equal 0, in two- and three-color QCD, exploring the gap 's sensitivity to the nature of the quark-quark interaction. The two-color theory, QC(2)D, is an excellent exemplar; the order of truncation of the qu ark-quark scattering kernel K has no qualitative impact, which allows a str aightforward elucidation of the effects of mu when the coupling is strong. in the three-color theory the rainbow-ladder truncation admits diquark boun d states, a defect that is eliminated by an improvement of K. The corrected gap equation describes a superfluid phase that is semiquantitatively simil ar to that obtained using the rainbow truncation. A model study suggests th at the width of the superfluid gap and the transition point in QC(2)D provi de reliable quantitative estimates of those quantities in QCD. [S0556-2813( 99)07112-5].