title: Poynting theorem constraints on the signs of the imaginary parts of the electromagnetic constitutive parameters: comment.
abstract: Contrary to an unphysical conclusion obtained by Alavikia et al. [J. Opt. Soc. Am. A32, 522 (2015)JOAOD60740-323210.1364/JOSAA.32.000522], the imaginary parts of both the permittivity and the permeability of any linear, homogeneous, passive, spatially local, dielectric-magnetic material are always positive, independent of the signs of their real parts.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Depine
authors.forename: Akhlesh
authors.initials: A
authors.lastname: Lakhtakia