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Seminar information archive
Seminar information archive ～07/25｜Today's seminar 07/26 | Future seminars 07/27～
2025/07/25
Colloquium
15:30-16:30 Room #大講義室(auditorium) (Graduate School of Math. Sci. Bldg.)
Izumi Okada (Graduate School of Mathematical Sciences, The University of Tokyo)
Recent Advances in Simple Random Walks (日本語)
Izumi Okada (Graduate School of Mathematical Sciences, The University of Tokyo)
Recent Advances in Simple Random Walks (日本語)
[ Abstract ]
A simple random walk is a stochastic process in which, for example in two dimensions, the walker moves at each time step to one of the four neighboring sites—up, down, left, or right—with equal probability 1/4. Although this model has been extensively studied for many years, a number of fundamental questions remain unsolved even in such a simple setting.In this talk, I will provide an overview of recent developments in the field, along with some of our recent results.
A simple random walk is a stochastic process in which, for example in two dimensions, the walker moves at each time step to one of the four neighboring sites—up, down, left, or right—with equal probability 1/4. Although this model has been extensively studied for many years, a number of fundamental questions remain unsolved even in such a simple setting.In this talk, I will provide an overview of recent developments in the field, along with some of our recent results.
Algebraic Geometry Seminar
13:30-15:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Akihiro Kanemitsu (Tokyo Metropolitan University)
Quintic del Pezzo threefolds in positive and mixed characteristic
Akihiro Kanemitsu (Tokyo Metropolitan University)
Quintic del Pezzo threefolds in positive and mixed characteristic
[ Abstract ]
We will show that, over any base scheme, (families of) quintic del Pezzo threefolds V5 are classified by non-degenerate ternary symmetric bilinear forms.
As applications, we will discuss (1) the geometry of quintic del Pezzo threefolds in positive characteristic, especially in characteristic two, and (2) finiteness results of V5 over number fields/rings of integers.
(Based on joint work with Tetsushi Ito, Teppei Takamatsu, Yuuji Tanaka)
We will show that, over any base scheme, (families of) quintic del Pezzo threefolds V5 are classified by non-degenerate ternary symmetric bilinear forms.
As applications, we will discuss (1) the geometry of quintic del Pezzo threefolds in positive characteristic, especially in characteristic two, and (2) finiteness results of V5 over number fields/rings of integers.
(Based on joint work with Tetsushi Ito, Teppei Takamatsu, Yuuji Tanaka)
2025/07/22
Operator Algebra Seminars
16:45-18:15 Room #117 (Graduate School of Math. Sci. Bldg.)
Giovanni Ferrer (Ohio State University)
Higher quantum symmetries
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Giovanni Ferrer (Ohio State University)
Higher quantum symmetries
[ 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.
Alexis Marchand (Kyoto University)
Sharp spectral gaps for scl from negative curvature (ENGLISH)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Alexis Marchand (Kyoto University)
Sharp spectral gaps for scl from negative curvature (ENGLISH)
[ Abstract ]
Stable commutator length is a measure of homological complexity of group elements, with connections to many topics in geometric topology, including quasimorphisms, bounded cohomology, and simplicial volume. The goal of this talk is to shed light on some of its relations with negative curvature. We will present a new geometric proof of a theorem of Heuer on sharp lower bounds for scl in right-angled Artin groups. Our proof relates letter-quasimorphisms (which are analogues of real-valued quasimorphisms with image in free groups) to negatively curved angle structures for surfaces estimating scl.
[ Reference URL ]Stable commutator length is a measure of homological complexity of group elements, with connections to many topics in geometric topology, including quasimorphisms, bounded cohomology, and simplicial volume. The goal of this talk is to shed light on some of its relations with negative curvature. We will present a new geometric proof of a theorem of Heuer on sharp lower bounds for scl in right-angled Artin groups. Our proof relates letter-quasimorphisms (which are analogues of real-valued quasimorphisms with image in free groups) to negatively curved angle structures for surfaces estimating scl.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
thesis presentations
11:00-12:15 Room #118 (Graduate School of Math. Sci. Bldg.)
KATAYAMA Sho (東京大学大学院数理科学研究科)
On positive solutions to inhomogeneous elliptic problems
on unbounded domains
(非有界傾域上の非斉次楕円型問題の正値解について)
KATAYAMA Sho (東京大学大学院数理科学研究科)
On positive solutions to inhomogeneous elliptic problems
on unbounded domains
(非有界傾域上の非斉次楕円型問題の正値解について)
2025/07/15
Tuesday Seminar on Topology
17:00-18:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Anastasiia Tsvietkova (Rutgers University)
Polynomially many genus g surfaces in a hyperbolic 3-manifold (ENGLISH)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Anastasiia Tsvietkova (Rutgers University)
Polynomially many genus g surfaces in a hyperbolic 3-manifold (ENGLISH)
[ Abstract ]
For a low-dimensional manifold, one often tries to understand its intrinsic topology through its submanifolds, in particular of co-dimension 1. For example,
it was noticed before that presence of embedded essential surfaces in a 3-manifold can give information about that manifold. However to construct, classify or count such surfaces is a non-trivial task. We will discuss a universal upper bound for the number of non-isotopic genus g surfaces embedded in a hyperbolic 3-manifold, polynomial in hyperbolic volume. The surfaces are all closed essential surfaces, oriented and connected. This is joint work with Marc Lackenby.
[ Reference URL ]For a low-dimensional manifold, one often tries to understand its intrinsic topology through its submanifolds, in particular of co-dimension 1. For example,
it was noticed before that presence of embedded essential surfaces in a 3-manifold can give information about that manifold. However to construct, classify or count such surfaces is a non-trivial task. We will discuss a universal upper bound for the number of non-isotopic genus g surfaces embedded in a hyperbolic 3-manifold, polynomial in hyperbolic volume. The surfaces are all closed essential surfaces, oriented and connected. This is joint work with Marc Lackenby.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Tokyo-Nagoya Algebra Seminar
15:30-17:00 Online
Shunsuke Hirota (Kyoto University)
super category Oにおけるsemibrick (Japanese)
[ Reference URL ]
https://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Shunsuke Hirota (Kyoto University)
super category Oにおけるsemibrick (Japanese)
[ Reference URL ]
https://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Lie Groups and Representation Theory
14:30-15:30 Room #128 (Graduate School of Math. Sci. Bldg.)
Kazuki Kannaka (Kanazawa University)
Zariski-dense deformations of standard discontinuous groups for pseudo-Riemannian homogeneous spaces
Kazuki Kannaka (Kanazawa University)
Zariski-dense deformations of standard discontinuous groups for pseudo-Riemannian homogeneous spaces
[ Abstract ]
In higher-dimensional Riemannian compact locally symmetric spaces, rigidity theory has been developed by Selberg, Weil, Mostow, Margulis, and so on. On the other hand, since the late 1980s, Toshiyuki Kobayashi initiated the study of deformation theory for locally symmetric spaces beyond the Riemannian setting. In particular, a family of pseudo-Riemannian compact locally symmetric spaces of arbitrarily high dimension without local rigidity were discovered. In this talk, we focus on a class of pseudo-Riemannian compact locally symmetric spaces known as standard ones. We explore questions such as the following: (1) Do they possess local rigidity? (2) Can they be continuously deformed into non-standard ones? For example, we show that compact space forms of constant negative curvature with signature (4, 3) in dimension 7 admit continuous deformations, analogous to hyperbolic compact Riemann surfaces. These deformations are constructed using the bending construction, originally introduced by Thurston. This talk is based on joint work (arXiv:2507.03476) with Toshiyuki Kobayashi.
In higher-dimensional Riemannian compact locally symmetric spaces, rigidity theory has been developed by Selberg, Weil, Mostow, Margulis, and so on. On the other hand, since the late 1980s, Toshiyuki Kobayashi initiated the study of deformation theory for locally symmetric spaces beyond the Riemannian setting. In particular, a family of pseudo-Riemannian compact locally symmetric spaces of arbitrarily high dimension without local rigidity were discovered. In this talk, we focus on a class of pseudo-Riemannian compact locally symmetric spaces known as standard ones. We explore questions such as the following: (1) Do they possess local rigidity? (2) Can they be continuously deformed into non-standard ones? For example, we show that compact space forms of constant negative curvature with signature (4, 3) in dimension 7 admit continuous deformations, analogous to hyperbolic compact Riemann surfaces. These deformations are constructed using the bending construction, originally introduced by Thurston. This talk is based on joint work (arXiv:2507.03476) with Toshiyuki Kobayashi.
2025/07/14
Tokyo Probability Seminar
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Hirotatsu Nagoji (Kyoto University)
Singularity of solutions to singular SPDEs
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Hirotatsu Nagoji (Kyoto University)
Singularity of solutions to singular SPDEs
[ Abstract ]
We give a sufficient condition for the marginal distribution of the solution to singular SPDEs on the $d$-dimensional torus to be singular with respect to the law of the Gaussian measure induced by the corresponding linear equation. As applications we obtain the singularity of the $\phi^4_3$-quantum field measure with respect to the Gaussian free field measure and the border of parameters for the fractional $\phi^4$-measure to be singular with respect to the base Gaussian measure. Our approach is applicable to quite a large class of singular SPDEs. This talk is based on a joint work with S. Kusuoka (Kyoto University) and M. Hairer (EPFL).
We give a sufficient condition for the marginal distribution of the solution to singular SPDEs on the $d$-dimensional torus to be singular with respect to the law of the Gaussian measure induced by the corresponding linear equation. As applications we obtain the singularity of the $\phi^4_3$-quantum field measure with respect to the Gaussian free field measure and the border of parameters for the fractional $\phi^4$-measure to be singular with respect to the base Gaussian measure. Our approach is applicable to quite a large class of singular SPDEs. This talk is based on a joint work with S. Kusuoka (Kyoto University) and M. Hairer (EPFL).
Infinite Analysis Seminar Tokyo
15:30-16:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Danilo Lewański (University of Trieste)
A spin on Gromov-Witten / Hurwitz correspondence and integrability
(English)
Danilo Lewański (University of Trieste)
A spin on Gromov-Witten / Hurwitz correspondence and integrability
(English)
[ Abstract ]
Hurwitz numbers enumerate branched coverings of Riemann surfaces and provide a rich sandbox of examples for enumerative geometry and neighbouring areas. Surprisingly, there is a formula that connects them to the intersection theory of the moduli spaces of stable curves: the ELSV formula. Furthermore, these numbers enjoy an integrability of type 2D-Toda as they can be expressed as vacuum expectations in the Fock space, result that has been later employed in the GW/Hurwitz correspondence.
A spin-off from the research on the mirror symmetry on Calabi-Yau 3-folds led to the spin generation of Hurwitz numbers via topological recursion. Over time this result has been generalised in different directions, including the Hurwitz count of Riemann surfaces with a spin structure, which are conjecturally determining Gromov-Witten invariants of surfaces with smooth canonical divisor. This led once more to the link with integrability, this time of type BKP.
Hurwitz numbers enumerate branched coverings of Riemann surfaces and provide a rich sandbox of examples for enumerative geometry and neighbouring areas. Surprisingly, there is a formula that connects them to the intersection theory of the moduli spaces of stable curves: the ELSV formula. Furthermore, these numbers enjoy an integrability of type 2D-Toda as they can be expressed as vacuum expectations in the Fock space, result that has been later employed in the GW/Hurwitz correspondence.
A spin-off from the research on the mirror symmetry on Calabi-Yau 3-folds led to the spin generation of Hurwitz numbers via topological recursion. Over time this result has been generalised in different directions, including the Hurwitz count of Riemann surfaces with a spin structure, which are conjecturally determining Gromov-Witten invariants of surfaces with smooth canonical divisor. This led once more to the link with integrability, this time of type BKP.
2025/07/10
Geometric Analysis Seminar
14:00-15:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Jeff Viaclovsky (University of California, Irvine)
Fibrations on the $6$-sphere and Clemens threefolds (英語)
Jeff Viaclovsky (University of California, Irvine)
Fibrations on the $6$-sphere and Clemens threefolds (英語)
[ Abstract ]
Let $Z$ be a compact, connected $3$-dimensional complex manifold with vanishing first and second Betti numbers and non-vanishing Euler characteristic. We prove that there is no holomorphic mapping from $Z$ onto any $2$-dimensional complex space. In other words, $Z$ can only possibly fiber over a curve. This result applies in particular to a class of threefolds, known as Clemens threefolds, which are diffeomorphic to a connected sum of $k$ copies of $S^3 \times S^3$ for $k > 1$. This result also gives a new restriction on any hypothetical complex structure on the $6$-sphere $S^6$. This is joint work with Nobuhiro Honda.
Let $Z$ be a compact, connected $3$-dimensional complex manifold with vanishing first and second Betti numbers and non-vanishing Euler characteristic. We prove that there is no holomorphic mapping from $Z$ onto any $2$-dimensional complex space. In other words, $Z$ can only possibly fiber over a curve. This result applies in particular to a class of threefolds, known as Clemens threefolds, which are diffeomorphic to a connected sum of $k$ copies of $S^3 \times S^3$ for $k > 1$. This result also gives a new restriction on any hypothetical complex structure on the $6$-sphere $S^6$. This is joint work with Nobuhiro Honda.
2025/07/08
Numerical Analysis Seminar
16:30-18:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Masaki Imagawa (Kyoto Univsersity)
Convergence analysis of perturbed advection equations in a bounded domain (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Masaki Imagawa (Kyoto Univsersity)
Convergence analysis of perturbed advection equations in a bounded domain (Japanese)
[ Reference URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
Tuesday Seminar of Analysis
16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
Keisuke Takasao (Kyoto University)
Brakke's inequality and the existence of Brakke flow for volume preserving mean curvature flow (Japanese)
Keisuke Takasao (Kyoto University)
Brakke's inequality and the existence of Brakke flow for volume preserving mean curvature flow (Japanese)
[ Abstract ]
We consider the existence of the weak solutions to the volume preserving mean curvature flow. The Brakke flow defined using Brakke's inequality is well known as one of the weak solutions to the mean curvature flow. On the other hand, the volume preserving mean curvature flow has been studied via $L^2$-flow solution, BV solution, and flat flow, but the corresponding Brakke flow had not been considered so far. In this talk, we define the suitable Brakke flow for the volume preserving flow and show its global existence. This talk is based on joint works with Andrea Chiesa (University of Vienna).
We consider the existence of the weak solutions to the volume preserving mean curvature flow. The Brakke flow defined using Brakke's inequality is well known as one of the weak solutions to the mean curvature flow. On the other hand, the volume preserving mean curvature flow has been studied via $L^2$-flow solution, BV solution, and flat flow, but the corresponding Brakke flow had not been considered so far. In this talk, we define the suitable Brakke flow for the volume preserving flow and show its global existence. This talk is based on joint works with Andrea Chiesa (University of Vienna).
Lie Groups and Representation Theory
16:00-17:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Koichi Arashi (Tokyo Gakugei University)
On integral representations of reproducing kernels on quasi-symmetric Siegel domains
Koichi Arashi (Tokyo Gakugei University)
On integral representations of reproducing kernels on quasi-symmetric Siegel domains
[ Abstract ]
L.\ Schwartz established the foundational theory of reproducing kernels in the 1960s.
Around the same time, S.\ G.\ Gindikin obtained an explicit integral representation of the Bergman kernel for the Siegel domain of the second kind $\mathcal{S}(\Omega,Q)\subset U_{\mathbb C}\times V$.
This formula suggests that the set of irreducible unitary representations of the generalized Heisenberg group $G^{V}=U\rtimes V$ realized on this domain is embedded in the unitary dual of the group.
Such a notion of multiplicity-freeness property has since been reconsidered from a complex-geometric standpoint, motivated by Huckleberry–Wurzbacher's study of ``coisotropic actions'' and by T.\ Kobayashi's introduction of ``visible actions'', and its understanding continues to deepen.
In this talk, we focus on a quasi-symmetric Siegel domain, and for a real subspace $W\subset V$, study the representations of the subgroup $G^{W}=U\rtimes W$.
We show that the multiplicity-freeness property can be characterized both by geometric features of the group action and by the multiplicity-free irreducible decomposition of the unitary representation on the Bergman space.
L.\ Schwartz established the foundational theory of reproducing kernels in the 1960s.
Around the same time, S.\ G.\ Gindikin obtained an explicit integral representation of the Bergman kernel for the Siegel domain of the second kind $\mathcal{S}(\Omega,Q)\subset U_{\mathbb C}\times V$.
This formula suggests that the set of irreducible unitary representations of the generalized Heisenberg group $G^{V}=U\rtimes V$ realized on this domain is embedded in the unitary dual of the group.
Such a notion of multiplicity-freeness property has since been reconsidered from a complex-geometric standpoint, motivated by Huckleberry–Wurzbacher's study of ``coisotropic actions'' and by T.\ Kobayashi's introduction of ``visible actions'', and its understanding continues to deepen.
In this talk, we focus on a quasi-symmetric Siegel domain, and for a real subspace $W\subset V$, study the representations of the subgroup $G^{W}=U\rtimes W$.
We show that the multiplicity-freeness property can be characterized both by geometric features of the group action and by the multiplicity-free irreducible decomposition of the unitary representation on the Bergman space.
Tuesday Seminar on Topology
17:00-18:30 Room #hybrid/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Hiroki Ishikura (The University of Tokyo)
Stallings-Swan’s Theorem for Borel graphs (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Hiroki Ishikura (The University of Tokyo)
Stallings-Swan’s Theorem for Borel graphs (JAPANESE)
[ Abstract ]
A Borel graph is a simplicial graph on a standard Borel space X such that the edge set is a Borel subset of X^2. Such objects have been studied in the context of countable Borel equivalence relations, and recently there are many attempts to apply the ideas of geometric group theory to them. Stallings-Swan's theorem states that groups of cohomological dimension 1 are free groups. We will talk about an analog of this theorem for Borel graphs: A Borel graph on X with uniformly bounded degrees of cohomological dimension 1 is Lipschitz equivalent to a Borel acyclic graph on X. This is proved by establishing a criterion for certain decomposition of Borel graphs, which is inspired by Dunwoody's work on accessibility of groups.
[ Reference URL ]A Borel graph is a simplicial graph on a standard Borel space X such that the edge set is a Borel subset of X^2. Such objects have been studied in the context of countable Borel equivalence relations, and recently there are many attempts to apply the ideas of geometric group theory to them. Stallings-Swan's theorem states that groups of cohomological dimension 1 are free groups. We will talk about an analog of this theorem for Borel graphs: A Borel graph on X with uniformly bounded degrees of cohomological dimension 1 is Lipschitz equivalent to a Borel acyclic graph on X. This is proved by establishing a criterion for certain decomposition of Borel graphs, which is inspired by Dunwoody's work on accessibility of groups.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
thesis presentations
13:15-14:30 Room #128 (Graduate School of Math. Sci. Bldg.)
SATO Genki (東京大学大学院数理科学研究科)
Presentation of finite Reedy categories as localizations
of finite direct categories
(有限直圏の局所化としての有限Reedy圏の表示)
SATO Genki (東京大学大学院数理科学研究科)
Presentation of finite Reedy categories as localizations
of finite direct categories
(有限直圏の局所化としての有限Reedy圏の表示)
Tokyo-Nagoya Algebra Seminar
10:30-12:00 Online
Nao Mochizuki (Nagoya University)
On the Auslander—Reiten theory for extended hearts of proper connective DG-algebras (Japanese)
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
Nao Mochizuki (Nagoya University)
On the Auslander—Reiten theory for extended hearts of proper connective DG-algebras (Japanese)
[ Abstract ]
本講演では, proper connective DG代数のd-extended heartにおけるAuslander-Reiten理論 を紹介する.
講演の主な対象となるd-extended heartsは, コホモロジーが次数0から−d+1の間に集中するようなDG加群からなる導来圏の部分圏である. 特に, 有限次元代数の場合，1-extended heart は, 通常の有限生成加群圏に一致する.
本講演では，この有限生成加群圏におけるAuslander-Reiten理論が, d-extended hearts を用いることで proper connective DG代数の文脈にまで一般化されることを紹介する. また, DG-quiverから構成されるDG代数に対するAR-quiverの具体的な計算例も併せて紹介する.
Zoom ID 870 3048 1997 Password 392212
[ Reference URL ]本講演では, proper connective DG代数のd-extended heartにおけるAuslander-Reiten理論 を紹介する.
講演の主な対象となるd-extended heartsは, コホモロジーが次数0から−d+1の間に集中するようなDG加群からなる導来圏の部分圏である. 特に, 有限次元代数の場合，1-extended heart は, 通常の有限生成加群圏に一致する.
本講演では，この有限生成加群圏におけるAuslander-Reiten理論が, d-extended hearts を用いることで proper connective DG代数の文脈にまで一般化されることを紹介する. また, DG-quiverから構成されるDG代数に対するAR-quiverの具体的な計算例も併せて紹介する.
Zoom ID 870 3048 1997 Password 392212
http://www.math.nagoya-u.ac.jp/~aaron.chan/TNAseminar.html
2025/07/07
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Taiji Marugame (The Univ. of Electro-Communications)
Chains on twistor CR manifolds and conformal geodesics in dimension three (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
Taiji Marugame (The Univ. of Electro-Communications)
Chains on twistor CR manifolds and conformal geodesics in dimension three (Japanese)
[ Reference URL ]
https://forms.gle/gTP8qNZwPyQyxjTj8
Tokyo Probability Seminar
16:00-17:30 Room #126 (Graduate School of Math. Sci. Bldg.)
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Ryoji Takano (Osaka University)
A semigroup approach to the reconstruction theorem for singular modelled distributions and its application
We are having teatime from 15:15 in the common room on the second floor. Please join us.
Ryoji Takano (Osaka University)
A semigroup approach to the reconstruction theorem for singular modelled distributions and its application
[ Abstract ]
In our recent research, we extended a semigroup approach used in Otto & Weber (2019) and Hoshino (2023) to provide an alternative proof of the reconstruction theorem for singular modelled distributions. As an application, we constructed a local-in-time solution to the two-dimensional parabolic Anderson model with a non-translation-invariant differential operator. In this talk, I will introduce the idea of constructing solutions to singular SPDEs based on the theory of regularity structures and highlight the differences between our approach and previous works. I will then present main results of our study. This talk is based on joint work with Masato Hoshino (Institute of Science Tokyo).
In our recent research, we extended a semigroup approach used in Otto & Weber (2019) and Hoshino (2023) to provide an alternative proof of the reconstruction theorem for singular modelled distributions. As an application, we constructed a local-in-time solution to the two-dimensional parabolic Anderson model with a non-translation-invariant differential operator. In this talk, I will introduce the idea of constructing solutions to singular SPDEs based on the theory of regularity structures and highlight the differences between our approach and previous works. I will then present main results of our study. This talk is based on joint work with Masato Hoshino (Institute of Science Tokyo).
2025/07/04
thesis presentations
13:45-15:00 Room #128 (Graduate School of Math. Sci. Bldg.)
IMAI Koto (東京大学大学院数理科学研究科)
Ramification groups of Galois extensions over local fields of
positive characteristic with Galois group isomorphic to
the group of unitriangular matrices
(冪単三角行列の群と同型なGalois群を持つ正標数局所体上の
Galois拡大の分岐群)
IMAI Koto (東京大学大学院数理科学研究科)
Ramification groups of Galois extensions over local fields of
positive characteristic with Galois group isomorphic to
the group of unitriangular matrices
(冪単三角行列の群と同型なGalois群を持つ正標数局所体上の
Galois拡大の分岐群)
2025/07/03
Applied Analysis
16:00-17:30 Room #128 (Graduate School of Math. Sci. Bldg.)
Jessica Lin (McGill University)
Generalized Front Propagation for Stochastic Spatial Models (English)
Jessica Lin (McGill University)
Generalized Front Propagation for Stochastic Spatial Models (English)
[ Abstract ]
In this talk, I will present a general framework which can be used to analyze the scaling limits of various stochastic spatial "population" models. Such models include ternary Branching Brownian motion subject to majority voting and several interacting particle systems motivated by biology. The approach is based on moment duality and a PDE methodology introduced by Barles and Souganidis, which can be used to study the asymptotic behaviour of rescaled reaction-diffusion equations. In the limit, the models exhibit phase separation with an evolving interface which is governed by a global-in-time, generalized notion of mean-curvature flow. This talk is based on joint work with Thomas Hughes (University of Bath).
In this talk, I will present a general framework which can be used to analyze the scaling limits of various stochastic spatial "population" models. Such models include ternary Branching Brownian motion subject to majority voting and several interacting particle systems motivated by biology. The approach is based on moment duality and a PDE methodology introduced by Barles and Souganidis, which can be used to study the asymptotic behaviour of rescaled reaction-diffusion equations. In the limit, the models exhibit phase separation with an evolving interface which is governed by a global-in-time, generalized notion of mean-curvature flow. This talk is based on joint work with Thomas Hughes (University of Bath).
Tokyo Probability Seminar
16:00-17:30 Room #128 (Graduate School of Math. Sci. Bldg.)
The classroom is 128. This is a joint seminar with the Applied Analysis Seminar. No teatime today.
Jessica Lin (McGill University)
Generalized Front Propagation for Stochastic Spatial Models
The classroom is 128. This is a joint seminar with the Applied Analysis Seminar. No teatime today.
Jessica Lin (McGill University)
Generalized Front Propagation for Stochastic Spatial Models
[ Abstract ]
In this talk, I will present a general framework which can be used to analyze the scaling limits of various stochastic spatial "population" models. Such models include ternary Branching Brownian motion subject to majority voting and several interacting particle systems motivated by biology. The approach is based on moment duality and a PDE methodology introduced by Barles and Souganidis, which can be used to study the asymptotic behaviour of rescaled reaction-diffusion equations. In the limit, the models exhibit phase separation with an evolving interface which is governed by a global-in-time, generalized notion of mean-curvature flow. This talk is based on joint work with Thomas Hughes (University of Bath).
In this talk, I will present a general framework which can be used to analyze the scaling limits of various stochastic spatial "population" models. Such models include ternary Branching Brownian motion subject to majority voting and several interacting particle systems motivated by biology. The approach is based on moment duality and a PDE methodology introduced by Barles and Souganidis, which can be used to study the asymptotic behaviour of rescaled reaction-diffusion equations. In the limit, the models exhibit phase separation with an evolving interface which is governed by a global-in-time, generalized notion of mean-curvature flow. This talk is based on joint work with Thomas Hughes (University of Bath).
2025/07/02
Number Theory Seminar
17:00-18:00 Room #117 (Graduate School of Math. Sci. Bldg.)
Amoru Fujii (University of Tokyo)
Parametrization of supercuspidal representations of depth-zero for some simple adjoint groups (日本語)
Amoru Fujii (University of Tokyo)
Parametrization of supercuspidal representations of depth-zero for some simple adjoint groups (日本語)
[ Abstract ]
We construct a surjective map from the set of conjugacy classes of depth-zero enhanced L-parameters to that of isomorphism classes of depth-zero supercuspidal representations for simple adjoint groups, and check the bijectivity in various cases. We also prove that the Hiraga--Ichino--Ikeda conjecture on the formal degree of essentially square-integrable representations holds for this parametrization if it is bijective.
We construct a surjective map from the set of conjugacy classes of depth-zero enhanced L-parameters to that of isomorphism classes of depth-zero supercuspidal representations for simple adjoint groups, and check the bijectivity in various cases. We also prove that the Hiraga--Ichino--Ikeda conjecture on the formal degree of essentially square-integrable representations holds for this parametrization if it is bijective.
2025/07/01
Operator Algebra Seminars
16:45-18:15 Room #117 (Graduate School of Math. Sci. Bldg.)
Mao Hoshino (Univ. Tokyo)
A tensor categorical aspect of quantum group actions
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Mao Hoshino (Univ. Tokyo)
A tensor categorical aspect of quantum group actions
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Tuesday Seminar on Topology
17:00-18:00 Room #hybrid/056 (Graduate School of Math. Sci. Bldg.)
Pre-registration required. See our seminar webpage.
Genki Sato (Fcuro, Inc.)
Presentation of finite Reedy categories as localizations of finite direct categories (JAPANESE)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
Pre-registration required. See our seminar webpage.
Genki Sato (Fcuro, Inc.)
Presentation of finite Reedy categories as localizations of finite direct categories (JAPANESE)
[ Abstract ]
In this talk, we present a novel construction that, for a given Reedy category $C$, produces a direct category $\operatorname{Down}(C)$ and a functor $\operatorname{Down}(C) \to C$, exhibiting $C$ as an $(\infty,1)$-categorical localization of $\operatorname{Down}(C)$. This result refines previous constructions in the literature by ensuring that $\operatorname{Down}(C)$ is finite whenever $C$ is finite—a property not guaranteed by existing approaches, such as those by Lurie or by Barwick and Kan. As an intended future application, this finiteness property is expected to be useful for embedding the construction into the syntax of a (non-infinitary) logic. In particular, I expect that the construction may be used to develop a meta-theory of finitely truncated simplicial types and other finite Reedy presheaves for homotopy type theory, thereby extending Kraus and Sattler's unfinished approach. This talk is based on arXiv:2502.05096.
[ Reference URL ]In this talk, we present a novel construction that, for a given Reedy category $C$, produces a direct category $\operatorname{Down}(C)$ and a functor $\operatorname{Down}(C) \to C$, exhibiting $C$ as an $(\infty,1)$-categorical localization of $\operatorname{Down}(C)$. This result refines previous constructions in the literature by ensuring that $\operatorname{Down}(C)$ is finite whenever $C$ is finite—a property not guaranteed by existing approaches, such as those by Lurie or by Barwick and Kan. As an intended future application, this finiteness property is expected to be useful for embedding the construction into the syntax of a (non-infinitary) logic. In particular, I expect that the construction may be used to develop a meta-theory of finitely truncated simplicial types and other finite Reedy presheaves for homotopy type theory, thereby extending Kraus and Sattler's unfinished approach. This talk is based on arXiv:2502.05096.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
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