Calculation of Some Properties of Vacuum and π, σ Mesons in the Global Color Symmetry Model

Based on the quark propagator derived in the instanton dilute liquid approximation, the quark condensate , the mixed quark gluon condensate , the four-quark condensate and tensor, pion vacuum susceptibilities have been calculated at the mean-field level in a nonperturbative QCD model. The numerical results are compatible with the values obtained within other nonperturbative approaches. The calculated masses and decay constants of π and σ mesons are close to the experimental values. These results show that the instanton medium might be a good approximation of the QCD vacuum.