Effect of instantons on the short-distance structure of hadronic currents

The influence of the nonperturbative structure of the quantum-chromodynamic vacuum on the short-distance behavior of hadronic currents is discussed. The dilute-gas approximation is systematically used. We show how to calculate in this approximation arbitrary Green's functions and that the effects of tunneling (instantons) are summarized by an appropriate effective Lagrangian. These methods are applied to the two-point current correlation function, which is explicitly calculated in the dilute-gas approximation. We estimate the numerical size of the instanton effects for e+e- annihilation and find them to be strongly momentum dependent and large. The qualitative features of these corrections suggest an explanation of precocious scaling