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Future seminars
Seminar information archive ～12/02｜Today's seminar 12/03 | Future seminars 12/04～
2025/12/08
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Rei Murakami (Tohoku Univ.)
. (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
Rei Murakami (Tohoku Univ.)
. (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
2025/12/09
Tuesday Seminar of Analysis
16:00-17:30 Room # 002 (Graduate School of Math. Sci. Bldg.)
Marco Squassina (Università Cattolica del Sacro Cuore)
Log-concave solutions of the log-Schrodinger equation in a convex domain (English)
Marco Squassina (Università Cattolica del Sacro Cuore)
Log-concave solutions of the log-Schrodinger equation in a convex domain (English)
[ Abstract ]
First, we discuss some recent results on power concavity for certain classes of quasi-linear elliptic problems. We then turn our attention to a new problem involving the so-called log-Schrödinger equation, which cannot be addressed within the standard framework. To handle this, we introduce new techniques that lead to the existence of log-concave solutions to the log-Schrödinger equation in convex domains. Finally, we conclude with a brief discussion of (quantitative) partial concavity results for both elliptic and parabolic problems, as well as some perspectives on future developments concerning (quantitative) quasi-radiality results for problems in the ball.
First, we discuss some recent results on power concavity for certain classes of quasi-linear elliptic problems. We then turn our attention to a new problem involving the so-called log-Schrödinger equation, which cannot be addressed within the standard framework. To handle this, we introduce new techniques that lead to the existence of log-concave solutions to the log-Schrödinger equation in convex domains. Finally, we conclude with a brief discussion of (quantitative) partial concavity results for both elliptic and parabolic problems, as well as some perspectives on future developments concerning (quantitative) quasi-radiality results for problems in the ball.
Operator Algebra Seminars
16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)
Dan Voiculescu (UC Berkeley)
Around entropy in free probability theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Dan Voiculescu (UC Berkeley)
Around entropy in free probability theory
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Tuesday Seminar on Topology
17:00-18:30 Room #hybrid/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Yusuke Kuno (Tsuda University)
Emergent version of Drinfeld's associator equations (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Yusuke Kuno (Tsuda University)
Emergent version of Drinfeld's associator equations (JAPANESE)
[ Abstract ]
In 2012, Alekseev and Torossian proved that any solution of Drinfeld's associator equations gives rise to a solution of the Kashiwara-Vergne equations. Both equations arise in natural topological contexts. For the former, these are knots and braids in 3-space, and for the latter there are at least two contexts: one is the w-foams, a certain Reidemeister theory of singular surfaces in 4-space, and the other is the Goldman-Turaev loop operations on oriented 2-manifolds. With the hope of getting a better understanding of the relations among these topological objects, we introduce the concept of emergent braids, a low-degree Vassiliev quotient of braids over a punctured disk. Then we discuss a work in progress on the associated formality equations, the emergent version of Drinfeld's associator equations. This talk is partially based on a joint work with D. Bar-Natan, Z, Dancso, T. Hogan and D. Lin.
[ Reference URL ]In 2012, Alekseev and Torossian proved that any solution of Drinfeld's associator equations gives rise to a solution of the Kashiwara-Vergne equations. Both equations arise in natural topological contexts. For the former, these are knots and braids in 3-space, and for the latter there are at least two contexts: one is the w-foams, a certain Reidemeister theory of singular surfaces in 4-space, and the other is the Goldman-Turaev loop operations on oriented 2-manifolds. With the hope of getting a better understanding of the relations among these topological objects, we introduce the concept of emergent braids, a low-degree Vassiliev quotient of braids over a punctured disk. Then we discuss a work in progress on the associated formality equations, the emergent version of Drinfeld's associator equations. This talk is partially based on a joint work with D. Bar-Natan, Z, Dancso, T. Hogan and D. Lin.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Numerical Analysis Seminar
16:30-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)
Dorin Bucur (Université Savoie Mont Blanc)
On polygonal nonlocal isoperimetric inequalities: Hardy-Littlewood, Riesz, Faber-Krahn (English)
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Dorin Bucur (Université Savoie Mont Blanc)
On polygonal nonlocal isoperimetric inequalities: Hardy-Littlewood, Riesz, Faber-Krahn (English)
[ Abstract ]
The starting point is the Faber-Krahn inequality on the first eigenvalue of the Dirichlet Laplacian. Many refinements were obtained in the last years, mainly due to the use of recent techniques based on the analysis of vectorial free boundary problems. It turns out that the polygonal version of this inequality, very easy to state, is extremely hard to prove and remains open since 1947, when it was conjectured by Polya. I will connect this question to somehow easier problems, like polygonal versions of Hardy-Littlewood and Riesz inequalities and I will discuss the local minimality of regular polygons and the possibility to prove the conjecture by a mixed approach. This talk is based on joint works with Beniamin Bogosel and Ilaria Fragala.
[ Reference URL ]The starting point is the Faber-Krahn inequality on the first eigenvalue of the Dirichlet Laplacian. Many refinements were obtained in the last years, mainly due to the use of recent techniques based on the analysis of vectorial free boundary problems. It turns out that the polygonal version of this inequality, very easy to state, is extremely hard to prove and remains open since 1947, when it was conjectured by Polya. I will connect this question to somehow easier problems, like polygonal versions of Hardy-Littlewood and Riesz inequalities and I will discuss the local minimality of regular polygons and the possibility to prove the conjecture by a mixed approach. This talk is based on joint works with Beniamin Bogosel and Ilaria Fragala.
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
2025/12/10
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Paul Balmer (University of California, Los Angeles)
The spectrum of Artin motives
Paul Balmer (University of California, Los Angeles)
The spectrum of Artin motives
[ Abstract ]
In this joint work with Martin Gallauer, we investigate the tensor-triangular geometry of the category of Artin motives with coefficients of positive characteristic. This problem relates to modular representation theory of profinite groups and to the category of permutation modules. We shall explain some of the techniques that come into play in the study of the latter.
In this joint work with Martin Gallauer, we investigate the tensor-triangular geometry of the category of Artin motives with coefficients of positive characteristic. This problem relates to modular representation theory of profinite groups and to the category of permutation modules. We shall explain some of the techniques that come into play in the study of the latter.
2025/12/16
Numerical Analysis Seminar
16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Laurent Mertz (City University of Hong Kong)
A Control Variate Method Driven by Diffusion Approximation (English)
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Laurent Mertz (City University of Hong Kong)
A Control Variate Method Driven by Diffusion Approximation (English)
[ Abstract ]
We present a control variate estimator for a quantity that can be expressed as the expectation of a functional of a random process, that is itself the solution of a differential equation driven by fast mean-reverting ergodic forces. The control variate is the expectation of the same functional for the limit diffusion process that approximates the original process when the mean-reversion time goes to zero. To get an efficient control variate estimator, we propose a coupling method to build the original process and the limit diffusion process. We show that the correlation between the two processes indeed goes to one when the mean reversion time goes to zero and we quantify the convergence rate, which makes it possible to characterize the variance reduction of the proposed control variate method. The efficiency of the method is illustrated on a few examples. This is joint work with Josselin Garnier (École Polytechnique, France). Link to the paper: https://doi.org/10.1002/cpa.21976
[ Reference URL ]We present a control variate estimator for a quantity that can be expressed as the expectation of a functional of a random process, that is itself the solution of a differential equation driven by fast mean-reverting ergodic forces. The control variate is the expectation of the same functional for the limit diffusion process that approximates the original process when the mean-reversion time goes to zero. To get an efficient control variate estimator, we propose a coupling method to build the original process and the limit diffusion process. We show that the correlation between the two processes indeed goes to one when the mean reversion time goes to zero and we quantify the convergence rate, which makes it possible to characterize the variance reduction of the proposed control variate method. The efficiency of the method is illustrated on a few examples. This is joint work with Josselin Garnier (École Polytechnique, France). Link to the paper: https://doi.org/10.1002/cpa.21976
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Tuesday Seminar on Topology
17:00-18:00 Online
Pre-registration required. See our seminar webpage.
Tomoshige Yukita (Ashikaga University)
Continuity and minimality of growth rates of Coxeter systems (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Tomoshige Yukita (Ashikaga University)
Continuity and minimality of growth rates of Coxeter systems (JAPANESE)
[ Abstract ]
A pair (G, S) consisting of a group G and an ordered finite generating set S is called a marked group. On the set of all marked groups, one can define a distance that measures how similar the neighborhoods of the identity element in their Cayley graphs are. This space is called the space of marked groups. For a marked group, the function that counts the number of elements whose word length with respect to S is k is called the growth function, and the quantity describing its rate of divergence is called the growth rate. In this talk, we will discuss the continuity of the growth rate for marked Coxeter systems, and the problem of determining the minimal growth rate among Coxeter systems that are lattices in the isometry group of hyperbolic space.
[ Reference URL ]A pair (G, S) consisting of a group G and an ordered finite generating set S is called a marked group. On the set of all marked groups, one can define a distance that measures how similar the neighborhoods of the identity element in their Cayley graphs are. This space is called the space of marked groups. For a marked group, the function that counts the number of elements whose word length with respect to S is k is called the growth function, and the quantity describing its rate of divergence is called the growth rate. In this talk, we will discuss the continuity of the growth rate for marked Coxeter systems, and the problem of determining the minimal growth rate among Coxeter systems that are lattices in the isometry group of hyperbolic space.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
2025/12/19
Algebraic Geometry Seminar
13:30-15:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Hokuto Konno (University of Tokyo)
On diffeomorphisms of complex surfaces
Hokuto Konno (University of Tokyo)
On diffeomorphisms of complex surfaces
[ Abstract ]
Many basic questions about the diffeomorphism groups of complex surfaces remain unresolved. For example, until recently it was unknown whether there exists a simply-connected complex surface admitting a diffeomorphism that acts trivially on the intersection form but is not isotopic to the identity. We have recently answered this question by showing that certain elliptic surfaces do admit such diffeomorphisms. These diffeomorphisms are obtained as suitable compositions of reflections along (-2)-curves. Moreover, this result also provides a negative answer to a question of Donaldson in symplectic geometry. This talk is based on joint work with David Baraglia, and with Jianfeng Lin, Anubhav Mukherjee, and Juan Muñoz-Echániz.
Many basic questions about the diffeomorphism groups of complex surfaces remain unresolved. For example, until recently it was unknown whether there exists a simply-connected complex surface admitting a diffeomorphism that acts trivially on the intersection form but is not isotopic to the identity. We have recently answered this question by showing that certain elliptic surfaces do admit such diffeomorphisms. These diffeomorphisms are obtained as suitable compositions of reflections along (-2)-curves. Moreover, this result also provides a negative answer to a question of Donaldson in symplectic geometry. This talk is based on joint work with David Baraglia, and with Jianfeng Lin, Anubhav Mukherjee, and Juan Muñoz-Echániz.
2025/12/20
Seminar on Probability and Statistics
10:30-17:10 Room # (Graduate School of Math. Sci. Bldg.)
- (-)
- (-)
[ Reference URL ]
https://sites.google.com/view/yuimatutorial2025/
- (-)
- (-)
[ Reference URL ]
https://sites.google.com/view/yuimatutorial2025/
2025/12/22
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Keiji Oguiso (Univ. of Tokyo)
TBA (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
Keiji Oguiso (Univ. of Tokyo)
TBA (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
2025/12/26
Algebraic Geometry Seminar
13:30-15:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Nao Moriyama (Kyoto University)
TBA
Nao Moriyama (Kyoto University)
TBA
Colloquium
15:30-16:30 Room #NISSAY Lecture Hall (大講義室) (Graduate School of Math. Sci. Bldg.)
Tatsuro Kawakami (Graduate School of Mathematical Sciences, The University of Tokyo)
Singularities and differential forms in positive characteristic (日本語)
Tatsuro Kawakami (Graduate School of Mathematical Sciences, The University of Tokyo)
Singularities and differential forms in positive characteristic (日本語)
[ Abstract ]
In this talk, I will focus on the local aspects of differential forms on algebraic varieties. I begin by reviewing prior results in characteristic zero concerning the extension problem, which asks whether reflexive differential forms can be lifted to birational models such as resolutions of singularities. I will then introduce a new approach to the extension problem in positive characteristic using the Cartier operator. If time permits, I will also discuss a new class of singularities in positive characteristic, defined via the Cartier operator.
In this talk, I will focus on the local aspects of differential forms on algebraic varieties. I begin by reviewing prior results in characteristic zero concerning the extension problem, which asks whether reflexive differential forms can be lifted to birational models such as resolutions of singularities. I will then introduce a new approach to the extension problem in positive characteristic using the Cartier operator. If time permits, I will also discuss a new class of singularities in positive characteristic, defined via the Cartier operator.
2026/01/05
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Yasufumi Nitta (Tokyo Univ. of Science)
(Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
Yasufumi Nitta (Tokyo Univ. of Science)
(Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
2026/01/16
Algebraic Geometry Seminar
13:30-15:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Ryu Tomonaga (University of Tokyo)
TBA
Ryu Tomonaga (University of Tokyo)
TBA
