On electromagnetic fields in a linear medium with gyrotropic-like magnetoelectric properties

A linear, homogeneous medium, with D + (Combining low line sign)(r + (Combining low line sign)) = ε₌ · E + (Combining low line sign)(r + (Combining low line sign)) + (α₌ + σ + (Combining low line sign) × I₌) · H + (Combining low line sign)(r + (Combining low line sign)) and B + (Combining low line sign)(r + (Combining low line sign)) = μ₌ · H + (Combining low line sign)(r + (Combining low line sign)) + (β₌+ τ + (Combining low line sign) × I₌) · E + (Combining low line sign)(r + (Combining low line sign)) as its frequency-dependent constitutive relations, can be mapped into another linear, homogeneous medium with D + (Combining low line sign)′(r + (Combining low line sign)) = ε₌ · E + (Combining low line sign)′(r + (Combining low line sign)) + α₌ · H + (Combining low line sign)′(r + (Combining low line sign)) and B + (Combining low line sign)′(r + (Combining low line sign)) = μ₌ · H + (Combining low line sign)′(r + (Combining low line sign)) + β₌ · E + (Combining low line sign)′(r + (Combining low line sign)) as its constitutive relations, provided σ + (Combining low line sign) = -τ + (Combining low line sign). This mapping extends the scope of many extant results on radiation and propagation in linear media. We also delineate the relationship of the condition σ = -τ + (Combining low line sign) to the Post constraint that must be satisfied by the constitutive relations of all physical materials.