Semantics of dyadic and mixed potential field representation for 3-D current distributions in planar stratified media

The full spectral electric dyadic Green\´s function for three dimensional current distributions in planar stratified media can be obtained straight from Maxwell\´s equations. By following a physical reasoning analogous with the free space case but using general derivative relations for multilayered Green\´s functions, we derive a "basic" mixed potential form with a simple vector potential kernel but multiple scalar potential kernels, and also obtain the well established single scalar potential formulations with a dyadic vector potential kernel. Mixed potential forms are thus arrived at without the a priori introduction of scalar and vector potential, or choice of gauge condition. The nonuniqueness of the scalar potential kernel and the dyadic nature of the scalar and/or vector potentials are believed to be clarified by the proposed approach. A discussion of the different formulations focuses on physical meaning and numerical consequences for the solution of integral equations.