List of talks Winter Semester 2025/2026

October 17th 2025 - Rosa Preiß (Technische Universität Berlin), "New directions for signature varieties".

Abstract: Varieties of signature tensors were introduced by Améndola-Friz-Sturmfels in 2019. In this informal talk, I will give an overview of the works that followed this groundbreaking article, introduce the halfshuffle map M_p adjoint to a polynomial map p and hint current WIP.
Based on joint work with Annika Burmester, Steven Charlton, Laura Colmenarejo, Abhiram Kidambi, Felix Lotter. Special thanks to Francesco Galuppi.

October 22nd 2025 (at 9:00 am) - Jean Thibaut (CPT Marseille), "Generalized gauge theories on Lie algebroids".

Abstract: In this presentation we first introduce the formalism of Cartan geometry and present specific applications to describe gravitational theories by building action functionals from Characteristic classes and invariant polynomials.
In the second part we introduce the notion of generalized connections on Lie algebroids. We show they can be used to describe ordinary gauge theories (Ehresmann connections for particle physics and Cartan connections for gravitational theories) with a Higgs sector and the BRST formalism (used as a renormalization tool for the gauge theories) from a single unified mathematical structure corresponding to the Atiyah Lie algebroid of a principal bundle.

October 24th 2025 - Martin Geller (University of Oxford), "The Geometry of Rough Space".

Abstract: How can we differentiate functionals on rough path space? In this talk, I’ll be discussing how we can  approach this question, as well as some of my results.

October 29th 2025 (at 11:30 am) - Debjit Pal (Leibniz Universität Hannover), "Strong generalized holomorphic principal bundles".

Abstract: We explore a classical problem within the framework of generalized complex (GC) geometry, a structure introduced by Hitchin and further developed by Gualtieri and Cavalcanti - namely, the development of an appropriate bundle theory in this setting. In this talk, we present the theory of strong generalized holomorphic (SGH) principal bundles, along with their connections and curvatures. These bundles interpolate between holomorphic and flat symplectic bundles. This is a joint work with Mainak Poddar.

November 7th 2025 - Ko Sanders (Leibniz Universität Hannover), "TBA".

Abstract: TBA.

November 14th 2025 - Bin Zhang (Sichuan University), "TBA".

Abstract: TBA.

November 28th 2025 - Jan Mandrysch (IQOQI Wien), "TBA".

Abstract: TBA.

December 5th 2025 - Chuangzhong Li (Shandong University of Science and Technology), "TBA".

Abstract: TBA.

January 16th 2026 - Daan Janssen (University of York), "TBA".

Abstract: TBA.

January 23th 2026 - Janina Bernardy (MPI Bonn), "TBA".

Abstract: TBA.

January 23th 2026 - Malte Leimbach (MPI Bonn), "TBA".

Abstract: TBA.

January 29th 2026 (Joint session with the Geometry Seminar, at 16:15) - Claudio Dappiaggi (University of Pavia), "Equivalence between local and global Hadamard States with Robin boundary conditions on half-Minkowski spacetime".

Abstract: We construct the fundamental solutions and Hadamard states for a Klein-Gordon field in half-Minkowski spacetime with Robin boundary conditions in arbitrary dimensions using a generalisation of the Robin-to-Dirichlet map. On the one hand this allows us to prove the uniqueness and support properties of the Green operators. On the other hand, we obtain a local representation for the Hadamard parametrix that provides the correct local definition of Hadamard states, capturing `reflected' singularities from the spacetime timelike boundary. This allows us to prove the equivalence of our local Hadamard condition and the global Hadamard condition with a wave-front set described in terms of generalized broken bicharacteristics, obtaining a Radzikowski-like theorem in half-Minkowski spacetime. 

Joint work with B. Costeri, R. D. Singh and B. Juárez-Aubry -- ArXiv: 2509.26035 [math-ph]

January 30th 2026 - Beatrice Costeri (University of Pavia), "TBA".

Abstract: TBA.