Pion scattering and the skyrmion in ChPT with many pions

Abstract

The large N effective action of the non-linear sigma model based in the coset O(N+1)/O(N) is obtained. The renormalization of this effective action requires the introduction of an infinite set of counterterms. However, there exit particular cases where, at some scale, only a finite number of non-zero coupling constants are present. This fact makes possible a one parameter fit of the I=J=0 low-energy pion scattering. The corresponding non-local effective action is used to study the properties of the skyrmion which is shown to be unstable in this approximation.