2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/84468An electromagnetic trinity comprising vacuum, anti--vacuum, and nihility is postulated -- after making use of materials with "negative permittivity" and "negative permeability" -- to illuminate the structure of electromagnetic theory, at least insofar as the relationship of phase velocity with Poynting vector is concerned.5 pagesClassical Physicstext