As with any wave equation, these equations lead to two types of solution : advanced potentials ( which are related to the configuration of the sources at future points in time ), and retarded potentials ( which are related to the past configurations of the sources ); the former are usually disregarded where the field is to analyzed from a causality perspective.
12.
The solutions of Maxwell's equations in the Lorenz gauge ( see Feynman ) with the boundary condition that both potentials go to zero sufficiently fast as they approach infinity are called the retarded potentials, which are the magnetic vector potential and the electric scalar potential due to a current distribution of current density, charge density, and volume ?, within which " ? " and "'J "'are non-zero at least sometimes and some places ):
