Kl3Form Factors and Spectral Functions of Currents

Employing the usual techniques of the algebra of currents and the Weinberg spectralfunction sum rules, expressions are obtained relating the parameters ${\lambda }_{+}$, ${\lambda }_{-}$, and $\xi$ in $K_{l3\mathrm{}}$ decays. If one neglects the ($0^{+}$) kappa ($\kappa$) meson contribution, a comparatively large value of ${\lambda }_{-}$ (an order of magnitude larger than ${\lambda }_{+}$) is predicted. This is in agreement with the present experimental data. It is also shown that $\xi {\lambda }_{-}$ should be small and comparable with ${\lambda }_{+}$.