Pion scattering and the skyrmion in ChPT with many pions
  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. 
Antonio Dobado (Departament of Physics, Stanford University), Antonio   Lopez (Dept. Fisica Teorica, Univ. Complutense de Ma...