On the Legitimacy of an Assumption Underlying the Point-Matching Method (Correspondence and Author´s Reply)

The numerical solution of boundary value problems for the Helmholtz equation by the point-matching method presupposes the legitimacy of a specific representation of the solution. A necessary and sufficient condition is given for its validity. Earlier arguments purporting to show that the representation is valid only for circular cylinders, or for cylinders possessing certain symmetries, are shown to be unsound.