The mixed quark-gluon condensate from an effective quark-quark interaction

We exhibit the method for obtaining non-perturbative quark and gluonic vacuum condensates from a model truncation of QCD. The truncation allows for a phenomenological description of the quark-quark interaction in a framework which maintains all global symmetries of QCD and allows an 1NC expansion. Within this approach the functional integration over the gluon fields can be performed and therefore any gluonic vacuum observable can be expressed in terms of a quark operator and the gluon propagator. As a special case we calculate the mixed quark gluon condensate gs〈qGμνσμνq〉. We investigate how the value depends on the form of the model quark-quark interaction. A comparison with the results of quenched lattice QCD, the instanton liquid model and QCD sum rules is drawn.