**UBC Mathematics Department**

*http://www.math.ubc.ca*

## Colloquium Abstract: Professor Horst Knoerrer, Department of Mathematics, ETH, Zurich

*Evaluation of fermion loops by iterated residues*

Feynman diagrams are a tool used for identifying the dominant
behaviour of various complicated physical systems. First I will
explain the rules for building and computing Feynman diagrams
for many electron systems. Then I will focus on a particular
class of such diagrams (Fermion loops). The numerical evaluation
of Fermion loops for two-dimensional systems suggested some
surprising results. These are proven rigorously, using methods
of complex algebraic geometry.

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