Back in Italy

After about three weeks in a surprisingly warm Sweden I’m now back in Milan. This means that I’m also back in the office. While I feel I worked fairly decently in Sweden, its hard to compare it to actually sitting in an office. I wish I could show some progress from it tho…

At the moment I’m trying to compute some Feynman integrals. I’m working in two dimensions and have both vertex and box type diagrams with several different masses on the internal propagators. Following standard lore, a vertex and box type integral have three and four Feynman parameters respectively and it should be fairly straightforward to evaluate them analytically using Mathematica. It turns out its not. Even for the simpler vertex integrals its surprisingly tricky.

By now I’ve more or less given up on standard evaluation and turned to something called Mellin-Barnes representation. Here one trades the complexity of Feynman parameter integration to that of evaluating complex integrals. I spare you the technical details, but the work load is basically shifted to figuring out how the pole structure of Gamma functions looks like and then evaluating a combination of infinite sums. All in all still fairly complicated. As above, no progress. However, it is interesting to learn about the technique. Its fairly far away from the standard way to evaluate Feynman integrals…

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