Comment on "Poynting vector, heating rate, and stored energy in structured materials: A first principles derivation"

In this Comment I argue that Silveirinha's criticism of my earlier work [M.G.Silveirinha, Phys.Rev.B 80, 235120 2009)] is based on an unphysical excitation model which involves an "external current" which overlaps with a continuous medium but is not subject to constitutive relations. When this excitation model is replaced by the conventional and experimentally-relevant model of excitation by external electromagnetic fields, it can be easily shown that Silveirinha's formulas contain the very results he wanted to disprove. This and a few other misconceptions present in Silveirinha's paper are subject of this Comment.