Constraint on the Universal Function in Electroproduction

We show that analyticity and asymptotic behavior impose a severe contraint on the scale-invariant function widely suggested for the behavior of$\nu W_2\left(q^2\nu \right)$ as $q^2\to \infty$. If the asymptotic behavior of the off-mass-shell Compton scattering amplitude is dominated by the usual (nonfixed) Regge trajectories, then our constraint is violated by the experimental candidates for the $\nu W_2$ curve. On the other hand, the introduction of a fixed pole corresponding to the one used by Damashek and Gilman alters the constraint, which is then consistant with the 18° data.