RESONANCE CONTRIBUTIONS TO THE ELECTROMAGNETIC LOW-ENERGY CONSTANTS OF CHIRAL PERTURBATION-THEORY

The effective chiral Lagrangian of the strong and electromagnetic inte ractions of the pseudoscalar mesons at low energies depends on a set o f low energy constants, We determine the contributions to the electrom agnetic coupling constants at order O(e(2)p(2)), which arise from reso nances within a photon loop, We give some implications of our results, in particular we discuss in detail the effects on the corrections to Dashen's theorem. (C) 1997 Elsevier Science B.V.