Comments on "Variational Methods for Nonstandard Eigenvalue Problems in Waveguide and Resonator Analysis"

In his recent work, Linden proposes variational methods for so-called nonstandard eigenvalue problems with sweeping generalities. To be sure, unorthodox formulations and solution of broad classes of problems ought to be encouraged, provided that they are consistent and that they are cogently demonstrated to offer significant improvement over existing knowledge.