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Pion electromagnetic formfactor in the instanton vacuum

We have calculated the 3-point correlation function for the electromagnetic interaction of the pion in an ensembles of instantons and anti-instantons, modelling the QCD vacuum. The results are well described by a pion pole and the pion formfactor is extracted, nicely following a standard monopole fit. The experimental data on the formfactor are well reproduced, provided an average instanton size is fixed at ${\barρ}=0.35\pm 0.03\fm$, the same as found for a variety of other correlation functions and was found on the lattice.