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I. Current commutators in quantum electrodynamics. II. Electromagnetic mass differences of the pseudoscalar meson and baryon octets

This thesis is in two parts. In the first section, the operator 
structure of the singular terms in the equal-time commutator of space 
and time components of the electromagnetic current is investigated in 
perturbation theory by establishing a connection with Feynman diagrams. 
It is made very plausible that the singular term is a c number. Some 
remarks are made about the same problem in the electrodynamics of a 
spinless particle. In the second part, an SU(3) symmetric multi-channel calculation 
of the electromagnetic mass differences in the pseudoscalar meson and 
baryon octets is carried out with an attempt to include some of the 
physics of the crossed (pair annihilation) channel along the lines of 
the recent work by Ball and Zachariasen. The importance of the tensor 
meson Regge trajectories is emphasized. The agreement with experiment 
is poor for the isospin one mass differences, but excellent for 
those with isospin two.