Perturbation theory for coupled nonlinear Schrödinger equations

Abstract
We extend the perturbation theory of the nonlinear Schrödinger equation to the case of the integrable vector nonlinear Schrödinger equation. By applying the perturbed inverse scattering transform, we derive a set of nonlinear coupled evolution equations for the adiabatic change of the parameters of a vector soliton, in the presence of a generic perturbation. We show that the same equations may also be obtained by means of a Lagrangian variational approach. © 1996 The American Physical Society.