List of talks Summer Semester 2026

April 24th 2026 - Jan Mandrysch (IQOQI Wien), "How to measure quantum fields? Implementing a causal measurement scheme".

Abstract: While measurement processes in standard quantum mechanics are well understood, the extension of these ideas to quantum field theory (QFT) remains a key challenge. In particular, ensuring that measurements respect fundamental principles such as relativistic causality is crucial. A persistent issue concerning measurements in QFT is, though, that the usual axioms for QFT alone are insufficient to prevent superluminal signaling. In this talk, I will discuss a recent proposal by Fewster and Verch for a local, covariant and causal measurement framework in algebraic QFT. In particular, I will discuss completeness of the framework and motivate its underlying assumptions focussing on the concrete setting of a free scalar field and Gaussian measurements. We conclude that the Fewster-Verch approach is suitable to model typical measurements in QFT. 

The talk is based on joint work with Miguel Navascués (Lett Math Phys 115, 115 (2025), https://doi.org/10.1007/s11005-025-02001-3).

April 29th 2026 - Felix Medwed (Universität Potsdam), "The signature group for paths of higher variation as an inverse limit".

Abstract: E. Le Donne and R. Züst (2021) showed that the space of signatures of rectifiable paths is a geodesic metric tree. We extend their result originally formulated in terms of curve length to the setting of $p$-variation for $p>1$. This extension relies on results of Boedihardjo, Geng, Lyons, and Yang (2016) concerning signatures of weakly geometric rough paths, which provide the appropriate analytical control in the $p$-variation framework. The key components of the original construction are reinterpreted using the language of metric groups, allowing us to define and work with the signature group adapted to $p$-variation. Within this framework, we revisit the lifting procedure introduced by Le Donne and Züst—namely, the construction of a canonical lift of a path into a suitable group structure—and show that the main result, concerning the existence and properties of such lifts, continues to hold when length is replaced by $p$-variation.

May 15th 2026 (online) - Laios Zafeiriou (Aristotle University of Thessaloniki), "An Introduction to the Seiberg–Witten Equations" (CANCELLED).

Abstract: The Seiberg–Witten equations provide a powerful tool for studying the topology of smooth four-manifolds via gauge-theoretic methods. In this talk, we introduce the equations and the geometric framework in which they are defined, focusing on connections on line bundles, spin^c structures, and the associated Dirac operator. We then discuss the moduli space of solutions modulo gauge transformations and outline how Seiberg–Witten invariants arise from counting these solutions. Time permitting, we briefly mention some applications and connections to other approaches in four-manifold topology.

May 20th 2026 - Eva-Maria Hekkelman (MPI Bonn), "Unbounded operator integrals and Quantum Field Theory".

Abstract: Operator integrals appear in abundance in many areas of functional analysis. The typical way to deal with these is through a theory called Multiple Operator Integration (MOI). Noncommutative Geometry is no exception, but the involved operator arguments are here typically unbounded, and they do not neatly fit the usual theory of MOI. To solve this problem, in joint work with Edward McDonald and Teun van Nuland, we provided a construction of MOIs which can handle (unbounded) abstract pseudodifferential operators. I will sketch how this construction can play a role in a Quantum Field Theory model based on noncommutative geometry (through the spectral action). I will then discuss recent joint result with Teun van Nuland and Jesse Reimann regarding the power counting in this model.

Jul 3rd 2026 - Arne Hofmann (Leibniz Universität Hannover), "TBA".

Abstract: TBA.

Jul 8th 2026 - Alessandro Pietro Contini (Leibniz Universität Hannover), "TBA".

Abstract: TBA.