What is meant by self-energy? If you have an electron and it splits into an electron and a photon, and then recombines, this is called the self-energy, but how is this related to energy? This self-energy is infinite, but not after renormalization. However, this http://hitoshi.berkeley.edu/public_html/susy/susy.html" [Broken] claims that the self-energy is finite because an electron not only interacts with itself, but also the vacuum creates an electron/positron pair and a photon, so the original electron gets annihilated with the positron (along with the photon), leaving the vacuum electron which then becomes a real particle. These two processes cancel, so there is no self-energy. But how does this interpretation come out of quantum field theory? To me, diagrams b) and c) of the link are exactly the same, so not only can they not cancel, you can only take one of them. The only thing that I can think of when talking about canceling, are counter-terms. But this implies they're saying that renormalization has to do with creation of particles in vacuum, something I'm uncomfortable with - I think that's making up more than the equations actually say. Another thing that's problematic is that you aren't really calculating scattering wahen dealing with one initial particle and one final particle. You are calculating unscattering and I don't think the QFT scattering formulas apply. Isn't the probability just 1?