Date/Time : 08 Oct 2026 16:00
Venue : S17 #05-11 (Seminar Room 5)
Speaker : Kyu-Hwan Lee, University of Connecticut

In this talk, we first study murmurations in families of quadratic Dirichlet characters weighted by a smooth compactly supported function. We show that the murmuration density interpolates the phase transition in the one-level density of the associated symplectic family of $L$-functions. Next, we compute the murmuration density for the family of quadratic characters over function fields. We show that its expectation coincides with a correction term arising in the traces of high powers of Frobenius in this family, and we determine the large-genus asymptotics of this term. This correction term admits a description in terms of the stable homology of the moduli space of hyperelliptic curves of genus $g$ with a marked Weierstrass point.

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Date/Time : 07 Oct 2026 13:30
Venue : S16 #05-18
Speaker : Thomas Geisser, Rikkyo University

I will give an overview over properties of motivic cohomology theories and their applications to arithmetic and algebraic geometry. In particular, I plan to cover applications to formulas for special values of zeI will give an overview over properties of motivic cohomology theories and their applications to arithmetic and algebraic geometry. In particular, I plan to cover applications to formulas for special values of zeta-functions, class field theory of schemes, and duality for torsion sheaves.ta-functions, class field theory of schemes, and duality for torsion sheaves.

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Date/Time : 16 Sep 2026 13:30
Venue : S16 #05-18
Speaker : Teruhisa Koshikawa, Keio University

By the categorical local Langlands conjecture, the semiorthogonal decomposition indexed by the Kottwitz set and Bernstein decompositions in the geometric side are expected to have counterparts in the spectral side. I will discuss my joint work with Bertoloni Meli realizing them directly. It is closely related to the theory of cuspidal coherent sheaves, but also has connections to some recent developments in algebraic geometry.

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Date/Time : 09 Sep 2026 13:30
Venue : S16 #05-18
Speaker : Toshihisa Kubo, Ryukoku University

Let X be a smooth manifold and Y a smooth submanifold of X. Let G’ ⊂ G be Lie groups, with G acting on X and G’ acting on Y. A differential operator D from the space of smooth sections of a G-equivariant vector bundle over X and to that of a G’-equivariant vector bundle over Y is called a differential symmetry breaking operator (DSBO for short) if D is G’-intertwining.

In general, the classification and construction of DSBOs are challenging problems. Around 2010, Toshiyuki Kobayashi introduced a fascinating idea for addressing these problems when both X and Y are flag manifolds. We refer to the resulting machinery as the F-method. The F-method reduces the classification and construction of DSBOs to solving a certain system of partial differential equations via the algebraic Fourier transform of generalized Verma modules. In this talk, we shall first discuss recent progress on the F-method. We shall then give explicit formulas for the DSBOs for (G,G’)=(GL(3,R), GL(2,R)) with minimal parabolic subgroups. This talk is based on joint work with Jonathan Ditlevsen and Víctor Pérez-Valdés.

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Date/Time : 19 Aug 2026 13:30
Venue : S16 #05-18
Speaker : Liron Speyer, Okinawa Institute of Science and Technology

I will give a brief account of the combinatorial representation theory of type A Iwahori–Hecke algebras, and their realisation as cyclotomic KLR algebras. In this story, I will largely focus on the decomposition number problem as one of the key problems in this field, and James’s conjecture, which drove a lot of research until Williamson showed it to be false in 2013. While Williamson’s counterexample is incredibly large, and beyond explicit computation, I recently discovered a new counterexample, which is of minimal size. I will explain this counterexample in the talk, as well as touching on how I found it.

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Date/Time : 12 Aug 2026 13:30
Venue : S16 #05-18
Speaker : Dinesh S. Thakur, University of Rochester

After reviewing some basic facts of classical diophantine approximation, diophantine equations, we will discuss various analogs, contrasts, tools, and open questions in the finite characteristic situation.

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Date/Time : 27 Jul 2026 14:00
Venue : S17 #04-04 (Seminar Room 3)
Speaker : Pavel Turek, Okinawa Institute of Science and Technology

A central open problem of the modular representation theory of symmetric groups (and Hecke algebras) is the computation of decomposition numbers, which describe irreducible constituents of Specht modules in prime characteristic. These numbers are organised in a block matrix, called the decomposition matrix, whose structure remains a mystery. In this talk, we present new whole columns of this matrix labelled by a novel family of partitions called d-balanced partitions; this seems to be the first description of whole columns in each block to date! Depending on the number d, we either get an algebraic interpretation (for d=2, this is joint with David Hemmer) or characteristic-free columns applicable to Hecke algebras (for d>2, this is joint with Bim Gustavsson, Stacey Law, Lorenzo Putignano and Liron Speyer).

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Date/Time : 14 May 2026 14:00
Venue : S17 #04-05 (Seminar Room 2)
Speaker : Feiyue Huang, Beijing Normal University

In the study of blocks of Ariki–Koike algebras, the Uglov map—the essential link connecting multipartitions to partitions—originates from Frenkel’s level-rank duality of type $A^{(1)}$ affine Lie algebras on Fock space. Inspired by this result, we develop an analogous framework for each classical affine type once the corresponding level-rank duality is established. In this talk, we construct appropriate Fock spaces for all classical affine Lie algebras and introduce the associated combinatorial models, specifically Maya diagrams and abaci. By analyzing the action of the Virasoro algebra, we completely characterize the joint highest weight vectors in the Fock space, thereby formulating the corresponding level-rank duality theory. Using this new theory, we generalize the results of Fayers, Jacon-Lecouvey and Li-Qi et al. on block invariants of Ariki–Koike algebras, and provide combinatorial models for block invariants of cyclotomic KLR algebras for each classical affine type. This talk is based on a joint work with Wei Hu, Yanbo Li and Xiangyu Qi.

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Date/Time : 12 May 2026 14:00
Venue : S17 #05-12 (Seminar Room 4)
Speaker : LIU Jie, Chinese Academy of Sciences

I will report a joint work with Baohua Fu proving that most Hamiltonian reductions of cotangent bundles are affine closures of cotangent bundles, together with some applications.

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