Consider classical electron theory. Distinguish between the mechanical, electromagnetic, and observed electron mass. What is the degree of divergence of the classical electron self-energy?
What are the roles of mass-renormalization, runaway solutions, and preacceleration in classical electron...
What is electromagnetic duality for Maxwell's equations in free space without sources?
Is this symmetry valid when there are conventional sources? If not, what hypothetical additional sources are needed to restore duality symmetry?