The variational principle in dual relativistic electrodynamics

Relativistic electrodynamics is supplemented by the principle of equivalence of fields and currents, a generalization of the Love principle which is widely used in radiophysics. This is derived by requiring the invariance of the Lagrangian both to Lorentz transformations and to the duality transformation obtained from the generalized Larmor-Pistol'kors duality principle.