Is the free electromagnetic field a consequence of Maxwell´s equations or a postulate?

Abstract

It is generally accepted that solutions of so called “free” Maxwell equations for ϱ = 0 (null charge density at every point of the whole space) describe a free electromagnetic field for which flux lines neither begin nor end in a charge). In order to avoid ambiguities and unacceptable approximation which have place in the conventional approach in respect to the free field concept, we explicitly consider three possible types of space regions: (i) “isolated charge-free” region, where a resultant electric field with the flux lines which either begin or end in a charge is zero in every point, for example, inside a hollow conductor of any shape or in a free-charge universe; (ii) “non-isolated charge-free” region, where this electric [see (i)] field is not zero in every point; and (iii) “charge-neutral” region, where point charges exist but their algebraic sum is zero. According to these definitions a strict mathematical interpretation of Maxwell's equations gives following conclusions: (1) In “isolated charge-free” regions electric free field cannot be unconditionally understood neither as a direct consequence of Maxwell's equations nor as a valid approximation: it may be introduced only as a postulate; nevertheless, this case is compatible is the existence of a time-independent background magnetic field. (2) In both “charge-neutral” and “non-isolated charge-free” regions, where the condition ϱ = δ function or ϱ = 0 respectively holds, Maxwell's equation for the total electric field have non-zero solutions, as in the conventional approach. However, these solution cannot be strictly identified with the electric free field. This analysis gives rise to the reconsideration of the free-electromagnetic field concept and leads to the simplest implications in respect to charge-neutral universe.