We show that if a Hamiltonian symmetry is realized by Goldstone bosons then, in general, one does not expect the $S$-matrix and matrix elements of currents to be analytic functions of the symmetry-breaking parameters. This modifies the nonrenormalization theorems for vector form factors and some theorems of Dashen and Weinstein.

• Received 18 March 1971

DOI:https://doi.org/10.1103/PhysRevLett.26.1204