On the Marriage of Chiral Perturbation Theory and Dispersion Relations

Abstract

I describe the methodology for the use of dispersion relations in connection with chiral perturbation theory. The conditions for matching the two formalisms are given at $O(E^2)$ and $O(E^4)$. The two have several complementary features, as well as some limitations, and these are described by the use of examples, which include chiral sum rules related to the Weinberg sum rules, form factors, and a more complicated reaction, $γγ\rightarrow ππ$. (Invited talk presented at the International Workshop on Chiral Dynamics in Hadrons and Nuclei, Feb 6-10, 1995, Seoul, Korea)