Realizações não lineares da simetria quiral

Abstract

We study possible nonlinear realizations of chiral symmetry only in terms of isospin multiplets of the fields under consideration, isospin matrices and of the pion field, following closely the paper "Nonlinear Realizations of Chiral Symmetry", by Steven Weinberg, a traditional reference on this issue. Chiral invariant Lagrangians can be obtained from the construction of isoinvariant functions of the fields under consideration, its covariant derivatives and of the covariant derivative of the pion field. Such realizations do not allow mass to the pion, thus, in order to have massive pions, it is necessary to add symmetry breaking terms in the Lagrangian.