ABSTRACT
One very powerful way of experimentally investigating the strongly interacting particles (hadrons) is to look at them, to probe them with a known particle; in particular the photon. This permits a much finer control of variables, and probably decreases the theoretical complexity of the interactions. This chapter shows that the vector potential a is an arbitrary function of space and time. There are some special technical difficulties coming from the highly divergent nature of some of the expressions so mathematical rigor requires a little more attention. Gell-Mann's equal time commutator relations represent the first guessed dynamical property of hadrons that is not simply a consequence of relativistic quantum mechanics general principles.
