2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/223237A negative-phase-velocity condition derived by Depine and Lakhtakia [Microwave Opt Technol Lett 41 (2004) 315] for isotropic, homogeneous, passive, dielectric-magnetic materials is inapplicable as a negative-refraction condition for active materials.replacement for preliminary version submitted earlier by errorOpticsOn the inapplicability of a negative-phase-velocity condition as a negative-refraction condition for active materialstext