Renormalization: Locality, Multiplicativity, and Birkhoff factorizations

03.07.2026, 11:00  –  Campus Golm, Building 9, Room 2.22 and via Zoom
Arbeitsgruppenseminar Analysis

Arne Hofmann (Universität Hannover)

I will discuss the interactions between three conditions that can be imposed on the renormalization of Feynman amplitudes.

The first is the Epstein--Glaser factorization condition. In Lorentzian signature, this condition encodes casuality, in Riemannian signature it encodes a strong form of locality. The second, known as "multiplicativity", means that counterterms can be absorbed into the Lagrangian of the theory. Finally, the Connes--Kreimer approach to renormalization is organized around the idea that the renormalized Feynman rules are given by a Birkhoff factorization on the group of characters on the Hopf algebra of Feynman graphs.

These three conditions represent different ways of thinking about renormalization that are sometimes in tension. Nevertheless, I will attempt to show how they can be reconciled.

For more information and log in details please contact Christian Molle.