Sum Rules for Virtual Compton Scattering of Pions

Sum rules for virtual Compton scattering of pions have been obtained by using the Weinberg sum rules. Saturation of the sum rules by $\pi$, $\omega$, $\phi$, $A_1$, and $A_2$ intermediate states is found to be still unsatisfactory, suggesting that the sum rules converge very slowly. Also, the connection between the calculation of Das et al. for the ${\pi }^{+}-{\pi }^0$ mass difference and those of the standard techniques is discussed and clarified.