A Conjugation Symmetry in Linear Electromagnetism, in Extension of Materials with Negative Real Permittivity and Permeability Scalars

If all space is occupied by a linear bianisotropic material — whether homogeneous or not — then the concurrent replacements of the permittivity and the impermeability tensors by the negatives of their respective complex conjugates and of the magnetoelectric tensors by their respective complex conjugates (in the Boys–Post representation) imply the conjugation of both E and H, in the absence of externally impressed sources. This conjugation symmetry in linear electromagnetism has observable consequences when the linear bianisotropic material occupies a bounded region.