Note on collective variable theory of nonlinear Schrödinger solitons

Inconsistencies arise in a recently developed collective variable theory of nonlinear Schrödinger solitons, as a result of a particular formulation of the energy-conservation principle in terms of the time derivative of the phase of the original field. We show that the inconsistencies are resolved either by correctly reformulating the energy-conservation principle or by directly averaging the nonlinear Schrödinger equation.