Fixed Pole in the Virtual Compton AmplitudeA2

Abstract

We suggest here the presence of a $J=0\mathrm{}$ fixed pole in the virtual Compton amplitude $A_2$ with a residue linear in the photon mass $q^2$ for all $q^2$. The resultant sum rule is found to be consistent with the on-mass-shell ($q^2=0\mathrm{}$) data, the scale-invariance requirement at $q^2\to \infty$, and the electron scattering data for intermediate $q^2$.