Effective quark interactions and QCD propagators

We compute the momentum dependence of the effective four quark interaction in QCD after integrating out the gluons. Our method is based on a truncation of exact renormalization group equations which should give reasonable results for momenta above the confinement scale. The difference between the four quark interaction and the heavy quark potential can be minimized for an optimal renormalization scheme in the Landau gauge. Within the momentum range relevant for quarkonia our results agree with phenomenological potentials. We also calculate the propagators for gluons and ghosts in the Landau gauge.