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Seminar information archive
Seminar information archive ～09/23｜Today's seminar 09/24 | Future seminars 09/25～
2026/09/10
Tokyo Probability Seminar
14:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
Lectures start earlier.
Sung-Soo Byun (Seoul National University) 14:00-15:30
Inhomogeneous Geometric Last Passage Percolation and the q-deformed Jacobi Unitary Ensemble
GIG random matrices and a Yang-Baxter extension of the Matsumoto-Yor property
Lectures start earlier.
Sung-Soo Byun (Seoul National University) 14:00-15:30
Inhomogeneous Geometric Last Passage Percolation and the q-deformed Jacobi Unitary Ensemble
[ Abstract ]
Since the pioneering work of Johansson, geometric last passage percolation (LPP) has become one of the central models in integrable probability, with many remarkable properties established over the past two decades. Most existing results, particularly those admitting explicit formulae, however, concern homogeneous environments. In this talk, I will discuss geometric LPP in a particular inhomogeneous environment. Our approach is based on a duality with a q-deformed analogue of the classical Jacobi unitary ensemble. Exploiting recent developments in the asymptotic spectral analysis of this random matrix model, I will present recent results on the law of large numbers, an explicit characterisation of the shape function, and the fluctuation behaviour of the last passage time.
Jacek Wesolowski (Warsaw University of Technology) 16:00-17:30Since the pioneering work of Johansson, geometric last passage percolation (LPP) has become one of the central models in integrable probability, with many remarkable properties established over the past two decades. Most existing results, particularly those admitting explicit formulae, however, concern homogeneous environments. In this talk, I will discuss geometric LPP in a particular inhomogeneous environment. Our approach is based on a duality with a q-deformed analogue of the classical Jacobi unitary ensemble. Exploiting recent developments in the asymptotic spectral analysis of this random matrix model, I will present recent results on the law of large numbers, an explicit characterisation of the shape function, and the fluctuation behaviour of the last passage time.
GIG random matrices and a Yang-Baxter extension of the Matsumoto-Yor property
[ Abstract ]
A map is independence preserving (IP) if there exists a product probability measure which is transferred by this map into to a product probability measures. Many classical examples of such maps and related probability laws are known probably the best known is the map (x,y)\mapsto (x+y, x-y) is an IP map for product of normal laws. Sasada and Uozumi (2024) identified IP a new family of parametric Yang-Baxter maps on positive quadrant together with related probability laws. In particular, the map H_{III,B}^{(\alpha,\beta)}, of this family was connected to the IP property of the GIG distributions. This IP property appears also naturally in probabilistic integrable models of discrete Korteweg de Vries type, as observed by Croydon and Sasada (2020). In the case of (\alpha,\beta)=(1,0), remarkably, this IP property reduces to the classical Matsumoto-Yor property rooted in the conditional structure of functionals of exponential Brownian motion.
We will propose an extension of H_{III,B}^{(\alpha,\beta)} to a Yang-Baxter map on the cone of symmetric positive definite matrices of a fixed dimension. We will show that this extended map preserves independence of GIG random matrices. We will present a proof that the matrix GIG distribution is characterized by the IP property of this map.
A map is independence preserving (IP) if there exists a product probability measure which is transferred by this map into to a product probability measures. Many classical examples of such maps and related probability laws are known probably the best known is the map (x,y)\mapsto (x+y, x-y) is an IP map for product of normal laws. Sasada and Uozumi (2024) identified IP a new family of parametric Yang-Baxter maps on positive quadrant together with related probability laws. In particular, the map H_{III,B}^{(\alpha,\beta)}, of this family was connected to the IP property of the GIG distributions. This IP property appears also naturally in probabilistic integrable models of discrete Korteweg de Vries type, as observed by Croydon and Sasada (2020). In the case of (\alpha,\beta)=(1,0), remarkably, this IP property reduces to the classical Matsumoto-Yor property rooted in the conditional structure of functionals of exponential Brownian motion.
We will propose an extension of H_{III,B}^{(\alpha,\beta)} to a Yang-Baxter map on the cone of symmetric positive definite matrices of a fixed dimension. We will show that this extended map preserves independence of GIG random matrices. We will present a proof that the matrix GIG distribution is characterized by the IP property of this map.
Infinite Analysis Seminar Tokyo
14:00-16:00 Room #123 (Graduate School of Math. Sci. Bldg.)
Motohico Mulase (UC Davis)
The SL(2) that relates Gaiotto's Conformal Limit and the Geometric Langlands Correspondence (English)
Motohico Mulase (UC Davis)
The SL(2) that relates Gaiotto's Conformal Limit and the Geometric Langlands Correspondence (English)
[ Abstract ]
The purpose of this talk is to show that Gaiotto's "conformal limit" construction of opers via the non-Abelian Hodge correspondence gives the same map that appears in the Geometric Langlands Correspondence for the case of opers. The resulting map is a unique canonical biholomorphic map from the moduli space of G-spectral curves to the moduli space of LG-opers, both defined over a smooth complex projective curve X with a complex simple algebraic group G and its Langlands dual LG.
The Structure of the Talk:
In the first hour of the talk I will present the main theorem and explain motivational materials, including:
・The differential equations interpreting the stability conditions in algebraic geometry of moduli spaces;
・Simpson's NAH map between the moduli spaces of Higgs bundles and connections on X;
・The moduli space of opers that forms a Lagrangian in the moduli space of local systems on X;
・From a spectral curve to an oper as a quantization procedure; and
・The idea of Gaiotto on taking a scaling limit of NAH that changes a transcendental topological map into a calculable algebraic map.
In the second hour, I will talk about the following subjects:
・The Geometric Langlands Correspondence for the case of opers due to Beilinson-Drinfeld;
・Kostant's TDS;
・The proof of Gaiotto's conformal limit for the case of sl(2);
・GLC for sl(2);
・The parallelism of these proofs going from sl(2) to the general case through Kostant's TDS.
The purpose of this talk is to show that Gaiotto's "conformal limit" construction of opers via the non-Abelian Hodge correspondence gives the same map that appears in the Geometric Langlands Correspondence for the case of opers. The resulting map is a unique canonical biholomorphic map from the moduli space of G-spectral curves to the moduli space of LG-opers, both defined over a smooth complex projective curve X with a complex simple algebraic group G and its Langlands dual LG.
The Structure of the Talk:
In the first hour of the talk I will present the main theorem and explain motivational materials, including:
・The differential equations interpreting the stability conditions in algebraic geometry of moduli spaces;
・Simpson's NAH map between the moduli spaces of Higgs bundles and connections on X;
・The moduli space of opers that forms a Lagrangian in the moduli space of local systems on X;
・From a spectral curve to an oper as a quantization procedure; and
・The idea of Gaiotto on taking a scaling limit of NAH that changes a transcendental topological map into a calculable algebraic map.
In the second hour, I will talk about the following subjects:
・The Geometric Langlands Correspondence for the case of opers due to Beilinson-Drinfeld;
・Kostant's TDS;
・The proof of Gaiotto's conformal limit for the case of sl(2);
・GLC for sl(2);
・The parallelism of these proofs going from sl(2) to the general case through Kostant's TDS.
2026/09/09
FJ-LMI Seminar
11:15-12:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Léo BÉNARD (CNRS FJ-LMI)
Character varieties of knots, and the Reidemeister torsion function (英語)
https://fj-lmi.cnrs.fr/seminars
Léo BÉNARD (CNRS FJ-LMI)
Character varieties of knots, and the Reidemeister torsion function (英語)
[ Abstract ]
I will mainly motivate the study of Reidemeister torsion from a historical perspective, and highlight some recent related results and questions.
[ Reference URL ]I will mainly motivate the study of Reidemeister torsion from a historical perspective, and highlight some recent related results and questions.
https://fj-lmi.cnrs.fr/seminars
FJ-LMI Seminar
15:00-16:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Warm Up Session of the Workshop on Polylogarithms
Herbert GANGL (Durham University)
Introduction to polylogarithms, with connections to number theory and algebraic $K$-theory (英語)
https://fj-lmi.cnrs.fr/wp-content/uploads/2026/09/Warm_up_session_schedule_and_abstracts.pdf
Warm Up Session of the Workshop on Polylogarithms
Herbert GANGL (Durham University)
Introduction to polylogarithms, with connections to number theory and algebraic $K$-theory (英語)
[ Abstract ]
In this survey talk we discuss several basic properties of classical polylogarithms
$$ \mathrm{Li}_m(z)=\sum_{k\geq1}\frac{z^k}{k^m}
$$
in the unit disc, for $m \geq 1$, leading up to a beautiful connection to the algebraic $K$-theory of number
fields, motivated by an attempt to find a suitable generalisation of Dirichlet’s celebrated class number
formula. Bloch initiated this for the dilogarithm, and Zagier extended it to higher polylogarithms. It
turns out that an arguably even more suitable class of functions to describe this connection involves
multiple polylogarithms (MPLs = nested sums of classical ones, in several variables $z_1, \ldots , z_d)$. If time
allows, we will also try to give a glimpse of Goncharov’s highly relevant “depth reduction conjecture”
for MPLs and what is known about it.
[ Reference URL ]In this survey talk we discuss several basic properties of classical polylogarithms
$$ \mathrm{Li}_m(z)=\sum_{k\geq1}\frac{z^k}{k^m}
$$
in the unit disc, for $m \geq 1$, leading up to a beautiful connection to the algebraic $K$-theory of number
fields, motivated by an attempt to find a suitable generalisation of Dirichlet’s celebrated class number
formula. Bloch initiated this for the dilogarithm, and Zagier extended it to higher polylogarithms. It
turns out that an arguably even more suitable class of functions to describe this connection involves
multiple polylogarithms (MPLs = nested sums of classical ones, in several variables $z_1, \ldots , z_d)$. If time
allows, we will also try to give a glimpse of Goncharov’s highly relevant “depth reduction conjecture”
for MPLs and what is known about it.
https://fj-lmi.cnrs.fr/wp-content/uploads/2026/09/Warm_up_session_schedule_and_abstracts.pdf
FJ-LMI Seminar
16:15-17:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Warm Up Session of the Workshop on Polylogarithms
Luc PIRIO (CNRS FJ-LMI)
Polylogarithms and Webs
[ Reference URL ]
https://fj-lmi.cnrs.fr/wp-content/uploads/2026/09/Warm_up_session_schedule_and_abstracts.pdf
Warm Up Session of the Workshop on Polylogarithms
Luc PIRIO (CNRS FJ-LMI)
Polylogarithms and Webs
[ Reference URL ]
https://fj-lmi.cnrs.fr/wp-content/uploads/2026/09/Warm_up_session_schedule_and_abstracts.pdf
2026/08/21
Algebraic Geometry Seminar
13:15-14:45 Room #128 (Graduate School of Math. Sci. Bldg.)
Heath Pearson (the University of Nottingham)
TBA
Heath Pearson (the University of Nottingham)
TBA
[ Abstract ]
TBA
TBA
2026/08/04
thesis presentations
16:15-17:30 Room #122 (Graduate School of Math. Sci. Bldg.)
朝永 龍 (東京大学大学院数理科学研究科)
d-Tilting bundles and applications to d-representation infinite algebras and non-commutative crepant resolutions
（d-傾束およびそのd-無限表現型代数と非可換クレパント特異点解消への応用）
朝永 龍 (東京大学大学院数理科学研究科)
d-Tilting bundles and applications to d-representation infinite algebras and non-commutative crepant resolutions
（d-傾束およびそのd-無限表現型代数と非可換クレパント特異点解消への応用）
2026/07/31
Algebraic Geometry Seminar
16:00-17:30 Room #118 (Graduate School of Math. Sci. Bldg.)
Adrian Langer (University of Warsaw)
Fundamental group schemes in positive characteristic and its
applications
Adrian Langer (University of Warsaw)
Fundamental group schemes in positive characteristic and its
applications
[ Abstract ]
The main goal of this talk is to study analogues of the topological
fundamental group for (possibly singular) algebraic varieties in
positive characteristic. I will focus on one such analogue, whose
category of representations is given by crystals on so called stratified
site of a variety X.
This is motivated by Grothendieck's version of the Riemann-Hilbert
correspondence, which states that for a proper complex, possibly
singular, variety the category of representations of the topological
fundamental group of the analytification of X is equivalent to the
category of crystals on the stratified site of X. In positive
characteristic, crystals on the stratified site can equivalently be
described as F-divided bundles. For smooth varieties, these objects have
been studied extensively by, among others, D. Gieseker, J. P. dos
Santos, H. Esnault, V. Mehta and V. Srinivas. In this talk, I will
discuss several properties of the fundamental group that are familiar
from the complex setting and show that they continue to hold in positive
characteristic, even for singular varieties. As an application, I will
prove that simply connected, proper, normal varieties in positive
characteristic admit no nontrivial F-divided bundles. This generalizes
an earlier result of H. Esnault and V. Mehta concerning smooth
projective varieties, and settles Gieseker's conjecture in a more
general setting. If time permits I will also discuss the relative
version of Gieseker's conjecture. Most of this work is joint with Lei
Zhang (SYSU, Zhuhai).
The main goal of this talk is to study analogues of the topological
fundamental group for (possibly singular) algebraic varieties in
positive characteristic. I will focus on one such analogue, whose
category of representations is given by crystals on so called stratified
site of a variety X.
This is motivated by Grothendieck's version of the Riemann-Hilbert
correspondence, which states that for a proper complex, possibly
singular, variety the category of representations of the topological
fundamental group of the analytification of X is equivalent to the
category of crystals on the stratified site of X. In positive
characteristic, crystals on the stratified site can equivalently be
described as F-divided bundles. For smooth varieties, these objects have
been studied extensively by, among others, D. Gieseker, J. P. dos
Santos, H. Esnault, V. Mehta and V. Srinivas. In this talk, I will
discuss several properties of the fundamental group that are familiar
from the complex setting and show that they continue to hold in positive
characteristic, even for singular varieties. As an application, I will
prove that simply connected, proper, normal varieties in positive
characteristic admit no nontrivial F-divided bundles. This generalizes
an earlier result of H. Esnault and V. Mehta concerning smooth
projective varieties, and settles Gieseker's conjecture in a more
general setting. If time permits I will also discuss the relative
version of Gieseker's conjecture. Most of this work is joint with Lei
Zhang (SYSU, Zhuhai).
2026/07/27
Tokyo Probability Seminar
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:20 in the common room on the second floor. Please join us.
Reo Tsuboya (Kyoto University)
Weak solution theory for the stochastic compressible Navier-Stokes equations with slip boundary conditions
We are having teatime from 15:20 in the common room on the second floor. Please join us.
Reo Tsuboya (Kyoto University)
Weak solution theory for the stochastic compressible Navier-Stokes equations with slip boundary conditions
[ Abstract ]
Navier-Stokes方程式は、粘性のある流体の運動を記述する方程式であり、流体力学だけでなく非線形偏微分方程式論においても中心的な研究対象である。確率論の文脈では、外部からの不確実な影響や微視的な揺らぎを記述するため、ノイズを含む確率Navier-Stokes方程式が研究されている。非圧縮性流体の解析は古くから盛んに行われてきた一方で、気体のように密度変化を伴う圧縮性流体の解析は、特に確率論において比較的新しく、現在も多くの課題が残されている。さらに、流体の解析において境界条件の選択は重要な意味をもつ。近年では、流体が境界面に沿って滑ることを許す滑り境界条件が、物理的に自然な境界条件の一つとして注目を集めている。以上の背景を踏まえ、本講演では、まず確率圧縮性Navier-Stokes方程式の構造について概説し、その後、滑り境界条件のもとでの弱解理論について、講演者の結果を紹介する。
Navier-Stokes方程式は、粘性のある流体の運動を記述する方程式であり、流体力学だけでなく非線形偏微分方程式論においても中心的な研究対象である。確率論の文脈では、外部からの不確実な影響や微視的な揺らぎを記述するため、ノイズを含む確率Navier-Stokes方程式が研究されている。非圧縮性流体の解析は古くから盛んに行われてきた一方で、気体のように密度変化を伴う圧縮性流体の解析は、特に確率論において比較的新しく、現在も多くの課題が残されている。さらに、流体の解析において境界条件の選択は重要な意味をもつ。近年では、流体が境界面に沿って滑ることを許す滑り境界条件が、物理的に自然な境界条件の一つとして注目を集めている。以上の背景を踏まえ、本講演では、まず確率圧縮性Navier-Stokes方程式の構造について概説し、その後、滑り境界条件のもとでの弱解理論について、講演者の結果を紹介する。
2026/07/23
thesis presentations
14:00-15:15 Room #122 (Graduate School of Math. Sci. Bldg.)
髙谷 悠太 (東京大学大学院数理科学研究科)
Moduli space of depth-zero level structures on local shtukas
（局所シュトゥーカの深度0レベル構造のモジュライ空間）
髙谷 悠太 (東京大学大学院数理科学研究科)
Moduli space of depth-zero level structures on local shtukas
（局所シュトゥーカの深度0レベル構造のモジュライ空間）
2026/07/21
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Yusuke Isono (RIMS, Kyoto Univ.)
Introduction to Tomita--Takesaki theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Yusuke Isono (RIMS, Kyoto Univ.)
Introduction to Tomita--Takesaki theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
2026/07/17
Colloquium
15:30-16:30 Room #NISSAY Lecture Hall (Graduate School of Math. Sci. Bldg.)
Hiroki Matui (Graduate School of Mathematical Sciences, The University of Tokyo)
Topological Full Groups and C*-Algebras Arising from Dynamical Systems (日本語)
Hiroki Matui (Graduate School of Mathematical Sciences, The University of Tokyo)
Topological Full Groups and C*-Algebras Arising from Dynamical Systems (日本語)
[ Abstract ]
From a minimal dynamical system on a Cantor set, one can construct a countably infinite group called the topological full group. This group has the remarkable property that its commutator subgroup is simple, and various dynamical systems thus give rise to infinite groups with interesting properties. Taking as a main example the Stein groups introduced by Stein in 1992, I will survey and discuss some recent developments in this area. Time permitting, I will also touch on connections with C*-algebras constructed from dynamical systems and their K-groups, as well as with the homology groups of the dynamical systems themselves.
From a minimal dynamical system on a Cantor set, one can construct a countably infinite group called the topological full group. This group has the remarkable property that its commutator subgroup is simple, and various dynamical systems thus give rise to infinite groups with interesting properties. Taking as a main example the Stein groups introduced by Stein in 1992, I will survey and discuss some recent developments in this area. Time permitting, I will also touch on connections with C*-algebras constructed from dynamical systems and their K-groups, as well as with the homology groups of the dynamical systems themselves.
2026/07/15
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Naoto Fukutomi (University of Tokyo)
Localization and coalescence of condensed ringed spaces
Naoto Fukutomi (University of Tokyo)
Localization and coalescence of condensed ringed spaces
[ Abstract ]
Gillam proved that the category of locally ringed spaces admits a fully faithful embedding into a certain category, which has a right adjoint that maps some simple objects to the spectra of rings. In this talk, we use condensed mathematics to define an analogous category and its coreflective full subcategories, and explain that one of their coreflections maps certain simple objects to the adic spectra of certain Huber pairs.
Gillam proved that the category of locally ringed spaces admits a fully faithful embedding into a certain category, which has a right adjoint that maps some simple objects to the spectra of rings. In this talk, we use condensed mathematics to define an analogous category and its coreflective full subcategories, and explain that one of their coreflections maps certain simple objects to the adic spectra of certain Huber pairs.
2026/07/14
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Hiroshi Ando (Chiba University)
Model theory and Connes' bicentralizer problem
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Hiroshi Ando (Chiba University)
Model theory and Connes' bicentralizer problem
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Lie Groups and Representation Theory
16:00-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Joint with Tuesday Seminar on Topology.
Yuichiro Tanaka (Graduate School of Mathematical Sciences, The University of Tokyo)
Visible actions of real reductive groups on complex algebraic varieties
Joint with Tuesday Seminar on Topology.
Yuichiro Tanaka (Graduate School of Mathematical Sciences, The University of Tokyo)
Visible actions of real reductive groups on complex algebraic varieties
[ Abstract ]
A unitary representation of a locally compact group is multiplicity-free if each irreducible representation appears at most once in its irreducible decomposition.
To provide a unified perspective on this property in the context of Lie group representations, T. Kobayashi introduced the theory of visible action for holomorphic actions of Lie groups on complex manifolds.
This approach enables us to understand many known examples uniformly and also leads to the discovery of new ones by utilizing Kobayashi’s propagation theorem of multiplicity-freeness property for visible actions.
In this talk, we will begin with the definition of visible action, illustrated with examples, and then explore some known results on classifications of visible actions and relationships among the coisotropicity, the sphericity and the visibility for group-actions on complex smooth algebraic varieties.
We will also discuss recent results based on unitary tricks for transferring properties of compact group-actions on complex flag manifolds to non-compact ones.
A unitary representation of a locally compact group is multiplicity-free if each irreducible representation appears at most once in its irreducible decomposition.
To provide a unified perspective on this property in the context of Lie group representations, T. Kobayashi introduced the theory of visible action for holomorphic actions of Lie groups on complex manifolds.
This approach enables us to understand many known examples uniformly and also leads to the discovery of new ones by utilizing Kobayashi’s propagation theorem of multiplicity-freeness property for visible actions.
In this talk, we will begin with the definition of visible action, illustrated with examples, and then explore some known results on classifications of visible actions and relationships among the coisotropicity, the sphericity and the visibility for group-actions on complex smooth algebraic varieties.
We will also discuss recent results based on unitary tricks for transferring properties of compact group-actions on complex flag manifolds to non-compact ones.
Tuesday Seminar on Topology
16:00-17:30 Room #hybrid/056 (Graduate School of Math. Sci. Bldg.)
Joint with Lie Groups and Representation Theory Seminar. See our seminar webpage.
Yuichiro Tanaka (The University of Tokyo)
Visible actions of real reductive groups on complex algebraic varieties (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Joint with Lie Groups and Representation Theory Seminar. See our seminar webpage.
Yuichiro Tanaka (The University of Tokyo)
Visible actions of real reductive groups on complex algebraic varieties (JAPANESE)
[ Abstract ]
A unitary representation of a locally compact group is multiplicity-free if each irreducible representation appears at most once in its irreducible decomposition. To provide a unified perspective on this property in the context of Lie group representations, T. Kobayashi introduced the theory of visible action for holomorphic actions of Lie groups on complex manifolds. This approach enables us to understand many known examples uniformly and also leads to the discovery of new ones by utilizing Kobayashi's propagation theorem of multiplicity-freeness property for visible actions. In this talk, we will begin with the definition of visible action, illustrated with examples, and then explore some known results on classifications of visible actions and relationships among the coisotropicity, the sphericity and the visibility for group-actions on complex smooth algebraic varieties. We will also discuss recent results based on unitary tricks for transferring properties of compact group-actions on complex flag manifolds to non-compact ones.
[ Reference URL ]A unitary representation of a locally compact group is multiplicity-free if each irreducible representation appears at most once in its irreducible decomposition. To provide a unified perspective on this property in the context of Lie group representations, T. Kobayashi introduced the theory of visible action for holomorphic actions of Lie groups on complex manifolds. This approach enables us to understand many known examples uniformly and also leads to the discovery of new ones by utilizing Kobayashi's propagation theorem of multiplicity-freeness property for visible actions. In this talk, we will begin with the definition of visible action, illustrated with examples, and then explore some known results on classifications of visible actions and relationships among the coisotropicity, the sphericity and the visibility for group-actions on complex smooth algebraic varieties. We will also discuss recent results based on unitary tricks for transferring properties of compact group-actions on complex flag manifolds to non-compact ones.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Koya Sakakibara (Kanazawa University)
A Stabilized Dual-SAV Parametric Finite Element Method for Constrained Geometric Flows of Planar Closed Curves (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Koya Sakakibara (Kanazawa University)
A Stabilized Dual-SAV Parametric Finite Element Method for Constrained Geometric Flows of Planar Closed Curves (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
2026/07/13
Seminar on Geometric Complex Analysis
10:30-12:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Shuho Kanda (The Univ. of Tokyo)
Holomorphic polynomial crystallographic actions of nilpotent groups (Japanese)
https://forms.gle/8ERsVDLuKHwbVzm57
Shuho Kanda (The Univ. of Tokyo)
Holomorphic polynomial crystallographic actions of nilpotent groups (Japanese)
[ Abstract ]
It is a natural and still open question whether every simply connected nilpotent Lie group endowed with a left-invariant complex structure is biholomorphic to $\mathbb{C}^n$. In this talk, we give an affirmative answer under the additional assumption that the complex structure is nilpotent. Moreover, we construct such a biholomorphism explicitly by polynomial maps in exponential coordinates. As a consequence, every lattice in such a Lie group admits a free, properly discontinuous and cocompact action on $\mathbb{C}^n$ by holomorphic polynomial automorphisms. We interpret this as a holomorphic analogue of polynomial crystallographic actions, namely actions on $\mathbb{R}^n$ by polynomial diffeomorphisms that are free, properly discontinuous and cocompact, as introduced by Dekimpe, Igodt, and Lee.
[ Reference URL ]It is a natural and still open question whether every simply connected nilpotent Lie group endowed with a left-invariant complex structure is biholomorphic to $\mathbb{C}^n$. In this talk, we give an affirmative answer under the additional assumption that the complex structure is nilpotent. Moreover, we construct such a biholomorphism explicitly by polynomial maps in exponential coordinates. As a consequence, every lattice in such a Lie group admits a free, properly discontinuous and cocompact action on $\mathbb{C}^n$ by holomorphic polynomial automorphisms. We interpret this as a holomorphic analogue of polynomial crystallographic actions, namely actions on $\mathbb{R}^n$ by polynomial diffeomorphisms that are free, properly discontinuous and cocompact, as introduced by Dekimpe, Igodt, and Lee.
https://forms.gle/8ERsVDLuKHwbVzm57
2026/07/08
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Vova Sosnilo (RIKEN iTHEMS)
Descent for algebraic K-theory of algebraic stacks
https://vova-sosnilo.com/
Vova Sosnilo (RIKEN iTHEMS)
Descent for algebraic K-theory of algebraic stacks
[ Abstract ]
Algebraic K-theory satisfies descent with respect to Nisnevich covers, which allows one to deduce global computations for schemes to the affine case. For algebraic stacks this is insufficient, since algebraic stacks with nontrivial stabilizers do not admit Nisnevich covers by affine schemes. However, a theorem of Deshmukh shows that any algebraic stack with separated diagonal admits a Nisnevich surjection from an affine scheme. The Atiyah—Segal completion theorem measures precisely the failure of algebraic K-theory to satisfy descent with respect to Nisnevich surjections. We show that it holds for ANS algebraic stacks of finite type over a field of characteristic 0 using trace methods and equivariant resolution of singularities. Time permitting, we discuss an ongoing work attempting to extend this result in characteristic p.
[ Reference URL ]Algebraic K-theory satisfies descent with respect to Nisnevich covers, which allows one to deduce global computations for schemes to the affine case. For algebraic stacks this is insufficient, since algebraic stacks with nontrivial stabilizers do not admit Nisnevich covers by affine schemes. However, a theorem of Deshmukh shows that any algebraic stack with separated diagonal admits a Nisnevich surjection from an affine scheme. The Atiyah—Segal completion theorem measures precisely the failure of algebraic K-theory to satisfy descent with respect to Nisnevich surjections. We show that it holds for ANS algebraic stacks of finite type over a field of characteristic 0 using trace methods and equivariant resolution of singularities. Time permitting, we discuss an ongoing work attempting to extend this result in characteristic p.
https://vova-sosnilo.com/
Tokyo-Nagoya Algebra Seminar
13:00-14:30 Online
Yuta Takaya (University of Tokyo)
Characteristic-free approaches around Yu's construction (Japanese)
https://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Yuta Takaya (University of Tokyo)
Characteristic-free approaches around Yu's construction (Japanese)
[ Abstract ]
Yu's construction is one of the most wide-ranging constructions of supercuspidal representations. Recently, Fintzen, Kaletha, and Spice introduced a quadratic twist of this construction to build stable L-packets, which also appears in the geometric realization via positive-depth Deligne-Lusztig induction. In this talk, I will present a direct approach to twisted Yu's construction and explain how to remove technical conditions on small primes in the theory of Yu's construction and positive-depth Deligne-Lusztig induction.
Zoom ID 882 6509 3568 Password 616173
[ Reference URL ]Yu's construction is one of the most wide-ranging constructions of supercuspidal representations. Recently, Fintzen, Kaletha, and Spice introduced a quadratic twist of this construction to build stable L-packets, which also appears in the geometric realization via positive-depth Deligne-Lusztig induction. In this talk, I will present a direct approach to twisted Yu's construction and explain how to remove technical conditions on small primes in the theory of Yu's construction and positive-depth Deligne-Lusztig induction.
Zoom ID 882 6509 3568 Password 616173
https://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
2026/07/07
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Nanami Hashimoto (Keio University)
Equivalence of categories of KK-theory or E-theory for $C^*$-algebras over topological spaces by reflection functors
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Nanami Hashimoto (Keio University)
Equivalence of categories of KK-theory or E-theory for $C^*$-algebras over topological spaces by reflection functors
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Tuesday Seminar on Topology
16:00-17:00 Online
Pre-registration required. See our seminar webpage.
Tatsuhiko Yagasaki (Kyoto Institute of Technology)
Topological properties of groups of volume-preserving diffeomorphisms and groups of uniform homeomorphisms (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Tatsuhiko Yagasaki (Kyoto Institute of Technology)
Topological properties of groups of volume-preserving diffeomorphisms and groups of uniform homeomorphisms (JAPANESE)
[ Abstract ]
This talk is a continuation of survey on topological properties of groups of homeomorphisms/diffeomorphisms on noncompact manifolds. As a subject related to ends of noncompact manifolds, we discuss volume transfer towards ends, which leads to the existence of continuous sections under the compact-open topology for the actions of diffeomorphism groups on the spaces of volume forms on noncompact manifolds (a noncompact version of Moser's theorem) and for the end charge homomorphisms introduced by Alpern and Prasad. We also give a brief survey on the local and end deformation properties in groups of uniform homeomorphisms on noncompact metric manifolds with the sup-metric.
[ Reference URL ]This talk is a continuation of survey on topological properties of groups of homeomorphisms/diffeomorphisms on noncompact manifolds. As a subject related to ends of noncompact manifolds, we discuss volume transfer towards ends, which leads to the existence of continuous sections under the compact-open topology for the actions of diffeomorphism groups on the spaces of volume forms on noncompact manifolds (a noncompact version of Moser's theorem) and for the end charge homomorphisms introduced by Alpern and Prasad. We also give a brief survey on the local and end deformation properties in groups of uniform homeomorphisms on noncompact metric manifolds with the sup-metric.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
2026/07/06
Seminar on Geometric Complex Analysis
10:30-12:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Xiaojun Wu (Tsukuba Univ.)
Generalised Ueda Obstruction Classes and Non-Semipositive Line Bundles (English)
https://forms.gle/8ERsVDLuKHwbVzm57
Xiaojun Wu (Tsukuba Univ.)
Generalised Ueda Obstruction Classes and Non-Semipositive Line Bundles (English)
[ Abstract ]
Serre’s classical example provides a fundamental instance of a nef but non-semipositive line bundle and motivated the analytic definition of nefness introduced by Demailly–Peternell–Schneider. Building on subsequent developments by Koike, the classical Ueda obstruction classes provide a natural criterion for non-semipositivity. In this talk, we introduce a natural generalisation of the Ueda obstruction classes that is always well defined and for which the Chern curvature naturally determines representatives. As an application, we obtain an elementary and systematic method for constructing nef but non-semipositive line bundles.
[ Reference URL ]Serre’s classical example provides a fundamental instance of a nef but non-semipositive line bundle and motivated the analytic definition of nefness introduced by Demailly–Peternell–Schneider. Building on subsequent developments by Koike, the classical Ueda obstruction classes provide a natural criterion for non-semipositivity. In this talk, we introduce a natural generalisation of the Ueda obstruction classes that is always well defined and for which the Chern curvature naturally determines representatives. As an application, we obtain an elementary and systematic method for constructing nef but non-semipositive line bundles.
https://forms.gle/8ERsVDLuKHwbVzm57
Tokyo Probability Seminar
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:20 in the common room on the second floor. Please join us.
Tadahisa Funaki (BIMSA)
Interface motion from non-gradient Glauber-Kawasaki dynamics
We are having teatime from 15:20 in the common room on the second floor. Please join us.
Tadahisa Funaki (BIMSA)
Interface motion from non-gradient Glauber-Kawasaki dynamics
[ Abstract ]
Motivated by the problem of dynamic phase transitions, we study the derivation of interface motion from non-gradient Glauber-Kawasaki dynamics. In the balanced case, the limiting interface evolves according to the anisotropic curvature flow, while in the unbalanced case it is governed by a geometric Hamilton-Jacobi equation. We establish this result as a quantitative hydrodynamic limit and, by applying the method of quantitative homogenization, obtain convergence rates. We also investigate fluctuations of the interface and derive a linear stochastic partial differential equation. This talk is partially based on several joint works with Chenlin Gu (Tsinghua U), Han Wang (Tsinghua U), Shuhan Zhou (Peking U), Hyunjoon Park (Meiji U), Claudio Landim (IMPA), Sunder Sethuraman (U Arizona).
Motivated by the problem of dynamic phase transitions, we study the derivation of interface motion from non-gradient Glauber-Kawasaki dynamics. In the balanced case, the limiting interface evolves according to the anisotropic curvature flow, while in the unbalanced case it is governed by a geometric Hamilton-Jacobi equation. We establish this result as a quantitative hydrodynamic limit and, by applying the method of quantitative homogenization, obtain convergence rates. We also investigate fluctuations of the interface and derive a linear stochastic partial differential equation. This talk is partially based on several joint works with Chenlin Gu (Tsinghua U), Han Wang (Tsinghua U), Shuhan Zhou (Peking U), Hyunjoon Park (Meiji U), Claudio Landim (IMPA), Sunder Sethuraman (U Arizona).
2026/07/03
Algebraic Geometry Seminar
13:15-14:45 Room #117 (Graduate School of Math. Sci. Bldg.)
Shou Yoshikawa (Institute of Science Tokyo)
Hodge–Tate splitting and Akizuki–Nakano vanishing
Shou Yoshikawa (Institute of Science Tokyo)
Hodge–Tate splitting and Akizuki–Nakano vanishing
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