Nucleon electric polarizability in soliton models and the role of the seagull terms

Abstract

The full Hamiltonian of the soliton models contains no electric seagull terms. Here it is shown that if one restricts the fields to the collective subspace then electric seagull terms are induced in the effective Hamiltonian. These effective seagull contributions are consistent with gauge invariance. They also reproduce the leading nonanalytic behavior of a large $N_c$ chiral perturbation theory calculation of the electric polarizability.