Hadronicτdecay, pion radiative decay, and pion polarizability

Using conserved vector current and the first Weinberg sum rule, it is shown that the "missing" 10% of the hadronic τ decay could come from the axial-vector current. This implies for π→eνγ decay, FA(0)FV(0)=0.50±0.15, and a charged-pion polarizability α_π=5×10^-42 cm³.