Implications of the ALEPH tau-lepton decay data for perturbative and nonperturbative QCD

We use ALEPH data on hadronic tau decays in order to calculate Euclidean co ordinate space correlation functions in the vector and axial-vector channel s. The linear combination V - A receives no perturbative contribution and i s quantitatively reproduced by the instanton liquid model. In the case of V + A the instanton calculation is in good agreement with the data once pert urbative corrections are included. These corrections clearly show the evolu tion of alpha (s). We also analyze the range of validity of the operator pr oduct expansion (OPE). We conclude that the range of validity of the OPE is limited to x less than or equal to 0.3 fm, whereas the instanton model des cribes the data over the entire range.