This thesis is in two parts. In the first section, the operatorstructure of the singular terms in the equal-time commutator of spaceand time components of the electromagnetic current is investigated inperturbation theory by establishing a connection with Feynman diagrams.It is made very plausible that the singular term is a c number. Someremarks are made about the same problem in the electrodynamics of aspinless particle.
In the second part, an SU(3) symmetric multi-channel calculationof the electromagnetic mass differences in the pseudoscalar meson andbaryon octets is carried out with an attempt to include some of thephysics of the crossed (pair annihilation) channel along the lines ofthe recent work by Ball and Zachariasen. The importance of the tensormeson Regge trajectories is emphasized. The agreement with experimentis poor for the isospin one mass differences, but excellent forthose with isospin two.
