ABSTRACT
With calculating the elements of the S-matrix in the QED, we may face three types of divergences: the UV-divergences, the IR-divergences, and singularities due to the coincidence of two or more poles in the integrand. Divergences of the last type may appear, for example, when for some special values of the particle momenta a multiparticle process may be subdivided into independent processes involving independent particle groups. Consideration of such divergences is beyond the scope of this book, and an interested reader may find the relevant information in Ref. [84]. The IR-divergences are also out of consideration because they have put emphasis in the previous Sections. Now our attention is focused on the UV-divergences, presenting much trouble indeed.
