Combinatorics Seminar - Joachim Kock

16:00-18:00

Speaker: Joachim Kock

Title: From Möbius inversion to renormalisation

Abstract: Although Möbius inversion originates in number theory, its standard formulation, due to Rota, is in the setting of posets, where it is about splitting of intervals. It has become a standard and widely used counting device in combinatorics and application areas. The goal of the talk is to show how a slight generalisation of the Möbius inversion principle can also explain (the algebraic aspect of) one of the main approaches to renormalisation of perturbative quantum field theories, the so-called BPHZ renormalisation (after Bogoliubov, Parasiuk, Hepp, and Zimmerman), in the Hopf-algebraic formulation due to Kreimer. In the talk, I will explain all the words above. (In particular, no prior knowledge of physics is assumed.)

Dietary info: the talk does not contain category theory.