Conclusion

Abstract

In this final chapter, various auxiliary techniques related to the expansion of Feynman diagrams in various limits of momenta and masses are first described: summation by Padé approximants, summing up expansions by guess, Taylor expansion in a mass diference, and a method of direct evaluation of general integrals appearing in contributions to the asymptotic expansions by use of IBP. An alternative approach within the strategy of expansion by regions, which is based on the alpha representation and thereby is manifestly independent of the choice of the loop momenta, is then described. I conclude by characterizing the present status of expansion by regions and giving some advice about its application.