Estimating condensates from the differene of τ branching fractions

The difference of τ partial decay widths into even and odd number of pions, Rτ,V−A, may be considered as another important constraint on the hadronic spectral function ϱV−A(S), in addition to four classic sum rules of current algebra. Within certain reasonable assumptions its value may be used to test the factorization hypothesis and estimate the contribution of dimension 6 condensates into the τ hadronic decay width.