Asymptotic Expansions Methodsand Applications

Feynman diagrams are the most important theoretical tool for particle physicists. They are an efficient link between theory and experiment. However, their translation into actual numerical predictions is often very tedious if not impossible. Huge efforts have been devoted to their evaluation, and several powerful methods have been developed to systemize their treatment. The more complex a Feynman diagram is, the more important is it to find approximation procedures that allow to solve the problem with finite but reasonable accuracy. In this paper we will describe methods that have been developed over the recent years in order to systematically expand Feynman diagrams in their external parameters.