Post's constraint for electromagnetic constitutive relations

A brief review is given of the Post symmetries and constraint for covariant electromagnetic constitutive relations which are linear in the fields E and B. Their extension to non-covariant constitutive relations which are linear also in space and time derivatives of E and B is discussed. The Post constraint is compared with published results from multipole theory. It is found that for time-dependent fields in non-magnetic and magnetic substances, and to electric octopole-magnetic quadrupole order. the constraint is satisfied and in agreement with experimental data. For static fields of the magnetoelectric effect, available data do not satisfy this constraint.