Calculation of Some Properties of Vacuum and π, σ Mesons in the Global Color Symmetry Model**The project supported in part by National Natural Science Foundation of China and Nanjing University Talent Development Foundation

Abstract

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.