Structure of pion photoproduction amplitudes

We derive and apply the finite energy sum rules to pion photoproduction. We evaluate the low-energy part of the sum rules using several state-of-the-art models. We show how the differences in the low-energy side of the sum rules might originate from different quantum number assignments of baryon resonances. We interpret the observed features in the low-energy side of the sum rules with the expectation from Regge theory. Finally, we present a model, in terms of a Regge-pole expansion, that matches the sum rules and the high-energy observables.