1 Fakultät für Physik, Universität Bielefeld,
D-33615 Bielefeld , Germany (e-mail:
2 Nuclear Physics Institute of Moscow State University, 119899 Moscow, Russian Federation (e-mail: email@example.com)
3 Institut für Physik, Universität Mainz, D-55099 Mainz, Germany (e-mail: firstname.lastname@example.org)
4 Department of Physics, University of California, San Diego, La Jolla, CA 92093-0319 USA
Received: 22 April 1997 / Published online: 20 February 1998
Two-loop vertex Feynman diagrams with infrared and collinear divergences are investigated by two independent methods. On the one hand, a method of calculating Feynman diagrams from their small momentum expansion  extended to diagrams with zero mass thresholds  is applied. On the other hand, a numerical method based on a two-fold integral representation is used , . The application of the latter method is possible by using lightcone coordinates in the parallel space. The numerical data obtained with the two methods are in impressive agreement.