Seminar

Seminar#

The work group Thiel (AGT) has a regular seminar/meeting called Representation Theory and Beyond. The seminar takes place every two weeks on Thursdays at 14:00 in room 48-436. Guests – as listeners or speaker – are always welcome. Below we list only the meetings with formal presentations. Presentations will be announced the Monday before. For notifications please subscribe to the mailing list.

Organizers: Prof. Dr. Ulrich Thiel, Dr. Giulia Iezzi, Dr. Raphaël Paegelow.

  • February 5, 2026: Torben Bürger (RPTU). A symplectic resolution of the binary tetrahedral group.

    Among the exceptional complex reflection groups, the binary tetrahedral group is the only one whose associated symplectic singularity by the action on the direct sum of a vector space and its dual admits a symplectic resolution. This was first shown by Bellamy, and an explicit resolution was later determined by Lehn and Sorger, whose work forms the basis for this presentation. Utilizing the computer algebra system OSCAR, we explicitly construct the quotient variety and identify specific Weil divisors derived from the group’s order-3 reflections. We demonstrate the computation of the blowup along these divisors via the Rees algebra, which establishes a partial resolution of the singularity. A detailed analysis of the resulting affine charts reveals that the remaining singularities are either of type A1​ or isomorphic to the symplectic S_3-quotient variety​. Finally, we prove that after blowing up the singular locus of the variety arising from the partial resolution, the whole construction indeed yields a symplectic smooth resolution of the quotient variety.

  • January 15, 2026: Dante Luber (Paderborn University). Computations with matroid realization spaces.

  • December 11, 2025. Fabian Mäurer (RPTU). What are unitary tensor categories?

  • November 27, 2025: Giulia Iezzi (RPTU). Matroids and matroid stratifications.

  • November 6, 2025: Peter Mader (University of Bonn). Invariance Properties of Davydov-Yetter Cohomology.

  • October 23, 2025: Raphaël Paegelow (RPTU). Davydov-Yetter cohomology and Ocneanu rigidity.

  • June 18, 2025: Raphaël Paegelow (University of Lille). Combinatorial correspondences between the Gieseker spaces and the block theory of Ariki-Koike algebras.

  • June 13, 2025: Giulia Iezzi (RWTH Aachen). Linear degenerations of Schubert varieties via quiver Grassmannians.

  • April 17, 2025: Fabian Mäurer (RPTU). Tensor MeatAxe: Irreduzibilität von Modulobjekten.

  • March 6, 2025: Igor Makhlin (TU Berlin). Poset polytopes in representation theory.

  • 13. February 2025: Cedric Brendel (RPTU). Condensed Mathematics & the Liquid Tensor Experiment.

  • January 30, 2025: Torben Bürger (RPTU). Das Shephard-Todd-Chevalley-Serre Theorem.

  • January 16, 2025: Tobias Metzlaff. Additive and Multiplicative Coinvariant Spaces of Weyl Groups.

  • December 19, 2024 : Tam Linke (RPTU). Ocneanu Rigidity II.

  • November 28, 2024: Tam Linke (RPTU). Ocneanu Rigidity.

  • July 18, 2024: Chiara Fend (RPTU). Persistent Homology for Stochastic Geometry and Spatial Statistics.

  • July 16, 2024: Tobias Metzlaff (RPTU). Painting the Euclidean space: spectral bounds for set avoiding graphs.

  • July 4, 2024: Fabian Mäurer (RPTU). On Fusion Categories, Their Centers and Module Categories.

  • April 11, 2024: Cailan Li (Columbia University). The Two-Color Ext Soergel Calculus.

  • February 29, 2024: Marion Boucrot (Université Grenoble Alpes). The relation between A-infinity morphisms and pre-Calabi-Yau morphisms.

  • January 25, 2024: Jonathan Gruber (University of York). Centers and centralizers in (double) affine Hecke algebras.

  • January 18, 2024: Sebastian Debus (TU Chemnitz). Specht Ideals.

  • December 7, 2023: Tobias Metzlaff (RPTU). Chromatic numbers of set avoiding graphs.

  • November 9, 2023: Liam Rogel (RPTU). Khovanov Homologie.

  • September 7, 2023: Tobias Metzlaff (RPTU). Real Quadratic Fields.

  • July 20, 2023: U;rich Thiel (RPTU). Split and non-split representations.

  • June 22, 2023: Johannes Schmitt (RPTU). Basiswissen: Gröbner, SAGBI, Khovanskii.

  • May 25, 2023: Tobias Metzlaff (RPTU). Symmetry in Trigonometric Optimization.

  • April 13, 2023: Tobias Metzlaff (RPTU). Polynomielle Optimierung.

  • March 16, 2023: Ulrich Thiel (RPTU): Hecke Algebras.

  • February 16, 2023: Fabian Mäurer (RPTU): Von Planaren Algebren und dem Haagerup Subfactor.

  • January 26, 2023: Tobias Metzlaff (RPTU). Diagonale Invariantentheorie.

  • January 12, 2023: Tobias Metzlaff (RPTU). Multiplikative Invariantentheorie.

  • December 8, 2022: Fabian Mäurer (RPTU). ZFC, ETCS und Typentheorie.

  • November 24, 2022: Johannes Schmitt (RPTU). Kaplanskys Vermutungen sind NP-schwer.

  • November 10, 2022: Erec Thorn (RPTU). Comodules, Coalgebras and Reconstruction.

  • October 13, 2022: Liam Rogel (RPTU). Monoide und ihre Darstellungen.

  • September 15, 2022: Fabian Mäurer (RPTU). Lean 4.

  • July 7, 2022: Dario Mathiä (RPTU). Kristallbasen und zelluläre Charaktere.

  • June 23, 2022: Erec Thorn (RPTU). Perfecting Group Schemes.

  • June 9, 2022: Maximilian Hauck (RPTU). Der Satz von Kronecker–Weber und explizite Klassenkörpertheorie.

  • May 19, 2022: Fabian Mäurer (RPTU). Tensorkategorien in Julia II.

  • May 12, 2022: Fabian Mäurer (RPTU). Tensorkategorien in Julia.

  • April 28, 2022: Erec Thorn (RPTU). Einführung in Ext-Gruppen.

  • March 17, 2022: Johannes Schmitt (RPTU). Köchervarietäten.

  • February 17, 2022: Marco Albert (RPTU). Implementierung von Iwahori-Hecke Algebren in Julia.

  • February 3, 2022: Maria Walch (RPTU). Grothendiecks Homotopie-Hypothese.

  • January 20, 2022: Mathias Neumann-Brosig (TU Braunschweig). Ein Algorithmus zur Bestimmung der Frattini Untergruppe polyzyklischer Gruppen.

  • December 2, 2021: Quang Le Duc (RPTU). The algebra of distributions on an affine group scheme.

  • November 18, 2021: Liam Rogel (RPTU). Die Temperley-Lieb-Kategorie und ihre Geheimnisse.

  • November 4, 2021: Dario Mathiä (RPTU). Nikolauskonferenz 2021 Probevortrag.

  • October 21, 2021: Erec Thorn (RPTU). Was ist eine zelluläre Algebra?

  • October 7, 2021. Dario Mathiä (RPTU). Erzeugende Funktionen.

  • September 23, 2021: Fabian Mäurer (RPTU). Modulare Tensorkategorien.

  • August 12, 2021: Johannes Schmitt (RPTU). Invariantentheorie.

  • July 15, 2021: Liam Rogel (RPTU). Der J-Ring und seine Kategorifizierung.

  • July 1, 2021: Tom Schmit (RPTU). Computations in Coxeter Groups.

  • June 17, 2021: Maria Walch (RPTU). Autoencoders, Time Series, and Visualizations.

  • May 6, 2021: Ulrich Thiel (RPTU). Zelluläre Algebren.

  • April 22, 2021:. Dario Mathiä (RPTU). Mastermind.

  • April 8, 2021: Ulrich Thiel (RPTU). Schneℓℓkurs in ℓ-adischer Kohomologie.

  • April 1, 2021: Quang Le Duc (RPTU). Introduction to Group Schemes.

  • March 25, 2021: Johannes Schmitt (RPTU). Cox Ringe.

  • March 11, 2021: Erec Thorn (RPTU). Einführung in die Komplexitätstheorie.

  • February 25, 2021: Dario Mathiä (RPTU). Das plaktische Monoid.

  • February 11, 2021: Cedric Brendel & Julian Scheinert (RPTU). Implementierung einer Chess-Engine.

  • December 17, 2020: Liam Rogel (RPTU). Die Zentrumskategorie.

  • November 26, 2020: Johannes Schmitt (RPTU). McKay-Korrespondenzen.

  • November 12, 2020: Erec Thorn (RPTU). Einführung in Soergel Bimoduln.

  • September 29, 2020: Ulrich Thiel (RPTU). Triangulierte Kategorien.

  • September 8, 2020: Johannes Schmitt (RPTU). Quotientenvarietäten.

  • August 24, 2020: Liam Rogel (RPTU). Die Kategorie G-äquivarianter Garben auf einer endlichen Menge.

  • August 11, 2020: Dario Mathiä (RPTU). Schur-Weyl-Dualität.

  • July 29, 2020: Mario Walch (RPTU). (Deep) Persistent Homology.

  • July 7, 2020: Liam Rogel (RPTU). Was ist eine Fusionskategorie?

  • June 23, 2020: Johannes Schmitt (RPTU). Die Divisorenklassengruppe.

  • June 9, 2020: Dario Mathiä (RPTU). Einführung in Matroide.