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I am a postdoctoral researcher in mathematics at University of Münster, working as part of the research group in Topology. Previously, I worked at Freie Universität Berlin.
My areas of interest include (higher) category theory, (higher) algebra and algebraic theories, topos theory, algebraic K-theory, (geometric) group and representation theory, homotopy theory, (differential) topology, topics related to categorical logic, as well as many surrounding fields.
I have also briefly worked as a data scientist, and I am curious about the fascinating recent developments in machine learning and quantum computing.
Emails:
Emails:
- georg.lehner (at) uni-muenster.de or
Mathematical Writings
Mathematical Writings
Measure theory via locales (in preparation)
Algebraic K-theory of coherent spaces (Preprint, submitted for publication 2025)
Norm and assembly for additive invariants of finite groups joint with Alex Müller and Holger Reich (in preparation)
Computing the negative K-theory of finite groups of order ≤100 (Preprint, submitted for publication 2024)
Group completion via the action ∞-category (Preprint, submitted for publication 2024)
The passage from the integral to the rational group ring in algebraic K-theory (Preprint, submitted for publication 2023)
PhD thesis under supervision of Prof. Holger Reich, Freie Universität Berlin. My thesis is centered around the question of understanding the map from the integral to the rational group ring in algebraic K-theory. Graduated November 22, 2021, Summa Cum Laude.
Masters thesis under supervision of Prof. Holger Reich and Prof. Gavril Farkas, Humboldt Universität zu Berlin, 2018
Talks given
Talks given
"Algebraic K-theory of coherent spaces" 8.9.2024 @Universität Hamburg Higher Structures (Gongshow talk)
"A locale-theoretic construction of the Lebesgue measure" 3.5.2025 @ 110th Peripatetic Seminar on Sheaves and Logic , Slides and Notes
"An approach to the Rosenberg conjecture" 10.1.2025 @Interactions between C*-algebraic KK-theory and homotopy theory, Slides
"Norm, assembly and coassembly" 28.10.2024 @Universität Münster, Oberseminar Topology, Notes
"Norm, assembly and coassembly" 10.9.2024 @"Dualizable Categories & Continuous K-Theory", MPIM, Bonn. Slides
"Norm, assembly and coassembly" 14.5.2024 @"From Analysis to Homotopy Theory", Greifswald. Slides
"Rigidity and the Rosenberg Conjecture" 27.4.2024 @33rd NRW Topology Meeting, University of Wuppertal
"Group Completion via the action ∞-category" 15.4.2024 @(∞,n)-Categories and their applications, Utrecht University
"Group completion of E_n - Spaces and infinite products" 8.2.2024, @University Regensburg
Research stay, 4-6.12.2023 @University Copenhagen
"The passage from the integral to the rational group ring in algebraic K-theory" 24.7.2023, @University Regensburg
"The Rosenberg Conjecture through the lens of solidification" 21.7.2023, @Potsdam University Notes
"The map K_0 ZG -> K_0 QG" 2021, @GROOT Summer Seminar 2021
"What is the point of pointless topology?" 2019, @Berlin Mathematical School's "What is...?" Seminar
"What is a topological surface?" 2018, @Berlin Mathematical School's "What is...?" Seminar
Additional Things
Additional Things
Teaching
Teaching
Summer Semester 2025
Algebra II, with Holger Reich
Seminar: Geometric Group Theory, with Elmar Vogt
Online-Seminar on the Baum-Connes conjecture, joint with Anupam Datta (Bonn) and Devarshi Mukherjee (Münster). (If you are interested in joining, ask me via email)
Winter Semester 2024/25
Analysis 3, with Holger Reich
Topology and Topoi, lecture series.
You can find handwritten lecture notes and exercise sheets by clicking the links.Online-Seminar on C*-Algebras and their K-theory, joint with Anupam Datta (Bonn) and Devarshi Mukherjee (Münster). (If you are interested, ask me via email for a Zoom-link and/or notes.)
Summer Semester 2024
Analysis 2, with Holger Reich
Seminar on Representation theory of finite groups, with Elmar Vogt
Winter Semester 2023/24
Analysis 1, with Holger Reich
Masterseminar on Algebraic K-Theory, with Elmar Vogt
Summer Semester 2023
Topology 3/Homotopy Theory, with Holger Reich
Masterseminar on Stable Homotopy Theory, with Elmar Vogt
Winter Semester 2022/23
Topology 2, with Holger Reich
Students
Students
Masters
Chris Huggle, 2025: Classification of exponentiable ∞-topoi
Vittorio di Fraia, 2024: K-Theory and Infinite Products
Bachelors
Emma Stingele, 2025: Symmetry groups of Tilings of the Hyperbolic Plane
Konstantin Roßberg, 2025: Morse Theory and Exotic Spheres
Laurin Geyer, 2024: Toeplitz operators and K-Theory
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