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Future seminars
Seminar information archive ～07/01｜Today's seminar 07/02 | Future seminars 07/03～
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
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).
2026/07/07
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
2026/07/13
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
2026/07/14
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Hiroshi Ando (Chiba University)
TBA
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Hiroshi Ando (Chiba University)
TBA
[ 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/
2026/07/17
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.
2026/07/21
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
