### Journée-séminaire de combinatoire

#### (équipe CALIN du LIPN, université Paris-Nord, Villetaneuse)

Le 22 mars 2011 à 15h30 en B311, Flavia Stan nous parlera de : A symbolic summation approach to Feynman integral calculus

Résumé : We discuss two methods based on Wilf-Zeilberger summation for the computation of Feynman parameter integrals. For the first method, the integrals are rewritten as multisums over hypergeometric terms to fit the input class of WZ-summation. These summation problems are highly nested sums with non-standard boundary conditions. They satisfy inhomogeneous recurrences containing sums of lower nested depth on the right-hand sides. These last recurrences can be solved recursively by Carsten Schneider's Sigma package. Another approach to evaluate Feynman integrals is by representing them as nested Mellin-Barnes integrals. We show how WZ-methods determine recurrences for contour integrals of this type, thus eliminating the need to find sum representations. This algorithmic technique is also applied to prove typical entries from the Gradshteyn-Ryzhik table of integrals using the Mellin transform method.

 Dernière modification : Wednesday 06 July 2011 Contact : Cyril.Banderier at lipn.univ-paris13.fr