written in the form [compare with (4a), (11)] equals (identically) zero by virtue of (15b) and (28), and it is possible to write explicit expression for effective potential A$_{g}$ , using Poincar´ e Lemma (see, for example, [14] or [15]): Analogous expression for effective potential B$_{e}$ may be written, if requirement (31) is met. We might do not introduce effective potentials A$_{g}$ and B$_{e}$ , but simply use expressions (34) and (35) in the expression for the full action (23); i.e. the action (23) is ordinary normal action – compare with the Rohrlich statement upper. According to the definition, effective vector-potential A i g depends on partial derivatives ∂ $^{l}$Bm g ; similarly, effective pseodovector-potential B i e depends on partial derivatives ∂ $^{l}$Am e . Consideration of the dependence of A i g on partial derivatives ∂ $^{l}$Bm g with a varying B$_{g}$ would lead to the occurrence of a term, linearly depending on the value of current density j$_{e}$ , in the right-hand part of equation (15b), and a similar term, linearly depending on the value of current density j$_{g}$ , would occur in the right-hand part of equation (4b). This contradicts our initial assumption that the electromagnetic field generated by electrical charges and the electromagnetic field generated by magnetic charges are described independently and, hence, with varying potentials A$_{e}$ and B$_{g}$ we should not vary the terms of full action, containing the effective potentials. In any case, the source-containing terms of equations (4b), (15b) make no sense to quantization of a free electromagnetic field in relativistic quantum field theory. Since a distinction between action (23) and an ordinary action without magnetic charges is not important from viewpoint of relativistic quantum field theory, the Feynman rules for III. MAGNETIC MONOPOLE IN RELATIVISTIC QUANTUM FIELD THEORY 9 A k g ( x ) = 1 ∫ 0 ζF ik A$_{g}$ ( ζx ) x$_{i}$ dζ = 1 2 1 ∫ 0 ζe $^{iklm}$F$_{B}$$_{g}$$_{lm}$ ( ζx ) x$_{i}$ dζ. (34) B k e ( x ) = 1 ∫ 0 ζF ik B$_{e}$ ( ζx ) x$_{i}$ dζ = 1 2 1 ∫ 0 ζe $^{iklm}$F$_{A}$$_{e}$$_{lm}$ ( ζx ) x$_{i}$ dζ (35) ∂F ⋆ ml A$_{g}$ ∂x l = ∂F ml B$_{g}$ ∂x l = 0 , (33)