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過去の記録 ～04/23｜本日 04/24 | 今後の予定 04/25～
2024年04月26日(金)
代数幾何学セミナー
14:00-15:30 数理科学研究科棟(駒場) 056号室
河上 龍郎 氏 (京都大学)
Frobenius stable Grauert-Riemenschneider vanishing fails (日本語)
河上 龍郎 氏 (京都大学)
Frobenius stable Grauert-Riemenschneider vanishing fails (日本語)
[ 講演概要 ]
We show that the Frobenius stable version of Grauert-Riemenschneider vanishing fails for a terminal 3-fold in characteristic 2. To prove this, we introduce the notion of $F_p$-rationality for singularities in positive characteristic, and prove that 3-dimensional klt singularities are $\mathbb F_p$-rational. I will also talk about the vanishing of $F_p$-cohomologies of log Fano threefolds. This is joint work with Jefferson Baudin and Fabio Bernasconi.
We show that the Frobenius stable version of Grauert-Riemenschneider vanishing fails for a terminal 3-fold in characteristic 2. To prove this, we introduce the notion of $F_p$-rationality for singularities in positive characteristic, and prove that 3-dimensional klt singularities are $\mathbb F_p$-rational. I will also talk about the vanishing of $F_p$-cohomologies of log Fano threefolds. This is joint work with Jefferson Baudin and Fabio Bernasconi.
談話会・数理科学講演会
15:30-16:30 数理科学研究科棟(駒場) 大講義室(auditorium)号室
本多正平 氏 (東京大学大学院数理科学研究科)
リーマン多様体とその極限 (JAPANESE)
本多正平 氏 (東京大学大学院数理科学研究科)
リーマン多様体とその極限 (JAPANESE)
[ 講演概要 ]
リーマン多様体全体にグロモフ・ハウスドルフ距離を使って位相を入れると，リーマン多様体を人とする町Aができる．その町Aの中で「リッチ曲率のコントロールが効いた人」からなる村Bを考える．講演者はこの村Bに興味がある．この村Bはグロモフ・ハウスドルフ距離に関してコンパクト化可能であることがグロモフによって示されていた．よってコンパクト化してしまいたくなるのでそうすることにして，それをCと書く．その境界C＼Bは町Aをはみ出している．よってそこに現れるのはもはや人(=リーマン多様体)ではない．例えば整数次元でないものが現れたり，特異点が稠密だったり，空でないどんな開集合の2次のベッチ数が無限大になったりすることがある．それがどれだけワイルドか，ワイルドでもどれくらいのことがわかるのかと思って調べると，なぜか村B全体のことがよくわかるようになってくる．このような流れの研究を多様体の収束・崩壊理論とよび，しばしばリーマン多様体の社会学と呼ばれることもある．本講演ではさまざまな分野と深い関わりを持つこの分野の最新状況について紹介する．
リーマン多様体全体にグロモフ・ハウスドルフ距離を使って位相を入れると，リーマン多様体を人とする町Aができる．その町Aの中で「リッチ曲率のコントロールが効いた人」からなる村Bを考える．講演者はこの村Bに興味がある．この村Bはグロモフ・ハウスドルフ距離に関してコンパクト化可能であることがグロモフによって示されていた．よってコンパクト化してしまいたくなるのでそうすることにして，それをCと書く．その境界C＼Bは町Aをはみ出している．よってそこに現れるのはもはや人(=リーマン多様体)ではない．例えば整数次元でないものが現れたり，特異点が稠密だったり，空でないどんな開集合の2次のベッチ数が無限大になったりすることがある．それがどれだけワイルドか，ワイルドでもどれくらいのことがわかるのかと思って調べると，なぜか村B全体のことがよくわかるようになってくる．このような流れの研究を多様体の収束・崩壊理論とよび，しばしばリーマン多様体の社会学と呼ばれることもある．本講演ではさまざまな分野と深い関わりを持つこの分野の最新状況について紹介する．
2024年04月30日(火)
作用素環セミナー
16:45-18:15 数理科学研究科棟(駒場) 126号室
Harshit Yadav 氏 (Univ. Alberta)
Non-semisimple modular tensor categories via local modules
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
Harshit Yadav 氏 (Univ. Alberta)
Non-semisimple modular tensor categories via local modules
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~yasuyuki/tokyo-seminar.htm
2024年05月01日(水)
代数学コロキウム
17:00-18:00 数理科学研究科棟(駒場) 117号室
松本晃二郎 氏 (東京大学大学院数理科学研究科)
On the potential automorphy and the local-global compatibility for the monodromy operators at p ≠ l over CM fields. (日本語)
松本晃二郎 氏 (東京大学大学院数理科学研究科)
On the potential automorphy and the local-global compatibility for the monodromy operators at p ≠ l over CM fields. (日本語)
[ 講演概要 ]
Let F be a totally real field or CM field, n be a positive integer, l be a prime, π be a cohomological cuspidal automorphic representation of GLn over F and v be a non-l-adic finite place of F. In 2014, Harris-Lan-Taylor-Thorne constructed the l-adic Galois representation corresponding to π. (Scholze also constructed this by another method.) The compatibility of this construction and the local Langlands correspondence at v was proved up to semisimplification by Ila Varma(2014), but the compatibility for the monodromy operators was known only in conjugate self-dual cases and some special 2-dimensional cases. In this talk, we will prove the local-global compatibility in some self-dual cases and sufficiently regular weight cases by using some new potential automorphy theorems. Moreover, if we have time, we will also prove the Ramanujan conjecture for the cohomological cuspidal automorphic representations of GL2 over F, which was proved in parallel weight cases by Boxer-Calegari-Gee-Newton-Thorne (2023).
Let F be a totally real field or CM field, n be a positive integer, l be a prime, π be a cohomological cuspidal automorphic representation of GLn over F and v be a non-l-adic finite place of F. In 2014, Harris-Lan-Taylor-Thorne constructed the l-adic Galois representation corresponding to π. (Scholze also constructed this by another method.) The compatibility of this construction and the local Langlands correspondence at v was proved up to semisimplification by Ila Varma(2014), but the compatibility for the monodromy operators was known only in conjugate self-dual cases and some special 2-dimensional cases. In this talk, we will prove the local-global compatibility in some self-dual cases and sufficiently regular weight cases by using some new potential automorphy theorems. Moreover, if we have time, we will also prove the Ramanujan conjecture for the cohomological cuspidal automorphic representations of GL2 over F, which was proved in parallel weight cases by Boxer-Calegari-Gee-Newton-Thorne (2023).
離散数理モデリングセミナー
13:00-15:00 数理科学研究科棟(駒場) 126号室
Jaume Alonso 氏 (Technische Universität Berlin)
Semitoric systems and their symplectic invariants (English)
Jaume Alonso 氏 (Technische Universität Berlin)
Semitoric systems and their symplectic invariants (English)
[ 講演概要 ]
Semitoric systems are a special class of completely integrable systems defined on four-dimensional symplectic manifolds. One of the reasons that make these systems interesting is their classification in terms of five symplectic invariants proposed by Pelayo and Vũ Ngọc. In the last years, many efforts have been made in order to extend this classification to broader settings, to generate more examples and to compute their invariants. In this talk we will discuss some of the most important properties of semitoric systems and introduce some families of systems with one and more focus-focus singularities. We will also show how the symplectic invariants of these systems change as we move the parameters of the families and how they can be computed using mathematical software.
This is a joint work with H. Dullin, S. Hohloch and J. Palmer.
Semitoric systems are a special class of completely integrable systems defined on four-dimensional symplectic manifolds. One of the reasons that make these systems interesting is their classification in terms of five symplectic invariants proposed by Pelayo and Vũ Ngọc. In the last years, many efforts have been made in order to extend this classification to broader settings, to generate more examples and to compute their invariants. In this talk we will discuss some of the most important properties of semitoric systems and introduce some families of systems with one and more focus-focus singularities. We will also show how the symplectic invariants of these systems change as we move the parameters of the families and how they can be computed using mathematical software.
This is a joint work with H. Dullin, S. Hohloch and J. Palmer.
2024年05月07日(火)
トポロジー火曜セミナー
17:00-18:00 オンライン開催
参加を希望される場合は、下記URLから参加登録を行って下さい。
Ingrid Irmer 氏 (南方科技大学)
The Thurston spine and the Systole function of Teichmüller space (ENGLISH)
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
参加を希望される場合は、下記URLから参加登録を行って下さい。
Ingrid Irmer 氏 (南方科技大学)
The Thurston spine and the Systole function of Teichmüller space (ENGLISH)
[ 講演概要 ]
The systole function $f_{sys}$ on Teichm\"uller space $\mathcal{T}_{g}$ of a closed genus $g$ surface is a piecewise-smooth map $\mathcal{T}_{g}\rightarrow \mathbb{R}$ whose value at any point is the length of the shortest geodesic on the corresponding hyperbolic surface. It is known that $f_{sys}$ gives a mapping class group-equivariant handle decomposition of $\mathcal{T}_{g}$ via an analogue of Morse Theory. This talk explains the relationship between this handle decomposition and the Thurston spine of $\mathcal{T}_{g}$.
[ 参考URL ]The systole function $f_{sys}$ on Teichm\"uller space $\mathcal{T}_{g}$ of a closed genus $g$ surface is a piecewise-smooth map $\mathcal{T}_{g}\rightarrow \mathbb{R}$ whose value at any point is the length of the shortest geodesic on the corresponding hyperbolic surface. It is known that $f_{sys}$ gives a mapping class group-equivariant handle decomposition of $\mathcal{T}_{g}$ via an analogue of Morse Theory. This talk explains the relationship between this handle decomposition and the Thurston spine of $\mathcal{T}_{g}$.
https://park.itc.u-tokyo.ac.jp/MSF/topology/TuesdaySeminar/index_e.html
2024年05月08日(水)
代数学コロキウム
17:00-18:00 数理科学研究科棟(駒場) 117号室
Xinyao Zhang 氏 (東京大学大学院数理科学研究科)
The pro-modularity in the residually reducible case (English)
Xinyao Zhang 氏 (東京大学大学院数理科学研究科)
The pro-modularity in the residually reducible case (English)
[ 講演概要 ]
For a continuous odd two dimensional Galois representation over a finite field of characteristic p, it is conjectured that its universal deformation ring is isomorphic to some p-adic big Hecke algebra, called the big R=T theorem. Recently, Deo explored the residually reducible case and proved a big R=T theorem for Q under the assumption of the cyclicity of some cohomology group. However, his method is unavailable for totally real fields since the assumption does not hold any longer. In this talk, we follow the strategy of the work from Skinner-Wiles and Pan on the Fontaine-Mazur conjecture and give a pro-modularity result for some totally real fields, which is an analogue to the big R=T theorem.
For a continuous odd two dimensional Galois representation over a finite field of characteristic p, it is conjectured that its universal deformation ring is isomorphic to some p-adic big Hecke algebra, called the big R=T theorem. Recently, Deo explored the residually reducible case and proved a big R=T theorem for Q under the assumption of the cyclicity of some cohomology group. However, his method is unavailable for totally real fields since the assumption does not hold any longer. In this talk, we follow the strategy of the work from Skinner-Wiles and Pan on the Fontaine-Mazur conjecture and give a pro-modularity result for some totally real fields, which is an analogue to the big R=T theorem.
2024年05月13日(月)
東京確率論セミナー
16:00-17:30 数理科学研究科棟(駒場) 126号室
Shuwen Lou 氏 (University of Illinois)
TBA
Shuwen Lou 氏 (University of Illinois)
TBA
複素解析幾何セミナー
10:30-12:00 数理科学研究科棟(駒場) 128号室
川上 裕 氏 (金沢大学)
Bloch-Ros principleとその曲面論への応用 (Japanese)
https://forms.gle/gTP8qNZwPyQyxjTj8
川上 裕 氏 (金沢大学)
Bloch-Ros principleとその曲面論への応用 (Japanese)
[ 講演概要 ]
有理型関数の値分布論と正規族の理論との間には，Bloch principleと呼ばれるある種の双対性が存在する．講演者は笠尾俊輔氏との共同研究で，ZalcmanとRosの研究をもとに，この双対性を曲面のGauss写像の値分布にまで拡張した"Bloch-Ros principle"と呼ぶ理論的枠組みを発見した．本講演では，笠尾氏との共著論文（arXiv:2402.12909）で記した"Bloch-Ros principle"の詳細を解説する．
[ 参考URL ]有理型関数の値分布論と正規族の理論との間には，Bloch principleと呼ばれるある種の双対性が存在する．講演者は笠尾俊輔氏との共同研究で，ZalcmanとRosの研究をもとに，この双対性を曲面のGauss写像の値分布にまで拡張した"Bloch-Ros principle"と呼ぶ理論的枠組みを発見した．本講演では，笠尾氏との共著論文（arXiv:2402.12909）で記した"Bloch-Ros principle"の詳細を解説する．
https://forms.gle/gTP8qNZwPyQyxjTj8
2024年05月14日(火)
解析学火曜セミナー
16:00-17:00 数理科学研究科棟(駒場) 128号室
対面・オンラインハイブリッド開催（今回は講演が2件あります）
Heinz Siedentop 氏 (LMU University of Munich)
The Energy of Heavy Atoms: Density Functionals (English)
https://forms.gle/ZEyVso6wa9QpNfxH7
対面・オンラインハイブリッド開催（今回は講演が2件あります）
Heinz Siedentop 氏 (LMU University of Munich)
The Energy of Heavy Atoms: Density Functionals (English)
[ 講演概要 ]
Since computing the energy of a system with $N$ particles requires solving a $4^N$ dimensional system of (pseudo-)differential equations in $3N$ independent variables, an analytic solution is practically impossible. Therefore density functionals, i.e., functionals that depend on the particle density (3 variables) only and yield the energy upon minimization, are of great interest.
This concept has been applied successfully in non-relativistic quantum mechanics. However, in relativistic quantum mechanics even the simple analogue of the Thomas-Fermi functional is not bounded from below for Coulomb potential. This problem was addressed eventually by Engel and Dreizler who derived a functional from QED. I will review some known mathematical properties of this functional and show that it yields basic features of physics, such as asymptotic correct energy, stability of matter, and boundedness of the excess charge.
[ 参考URL ]Since computing the energy of a system with $N$ particles requires solving a $4^N$ dimensional system of (pseudo-)differential equations in $3N$ independent variables, an analytic solution is practically impossible. Therefore density functionals, i.e., functionals that depend on the particle density (3 variables) only and yield the energy upon minimization, are of great interest.
This concept has been applied successfully in non-relativistic quantum mechanics. However, in relativistic quantum mechanics even the simple analogue of the Thomas-Fermi functional is not bounded from below for Coulomb potential. This problem was addressed eventually by Engel and Dreizler who derived a functional from QED. I will review some known mathematical properties of this functional and show that it yields basic features of physics, such as asymptotic correct energy, stability of matter, and boundedness of the excess charge.
https://forms.gle/ZEyVso6wa9QpNfxH7
解析学火曜セミナー
17:15-18:15 数理科学研究科棟(駒場) 128号室
対面・オンラインハイブリッド開催（今回は講演が2件あります）
Robert Laister 氏 (University of the West of England)
Well-posedness for Semilinear Heat Equations in Orlicz Spaces (English)
https://forms.gle/ZEyVso6wa9QpNfxH7
対面・オンラインハイブリッド開催（今回は講演が2件あります）
Robert Laister 氏 (University of the West of England)
Well-posedness for Semilinear Heat Equations in Orlicz Spaces (English)
[ 講演概要 ]
We consider the local well-posedness of semilinear heat equations in Orlicz spaces, the latter prescribed via a Young function $\Phi$. Many existence-uniqueness results exist in the literature for power-like or exponential-like nonlinearities $f$, where the natural setting is an Orlicz space of corresponding type; i.e. if $f$ is power-like then $\Phi$ is power-like (Lebesgue space), if $f$ is exponential-like then $\Phi$ is exponential-like. However, the general problem of prescribing a suitable $\Phi$ for a given, otherwise arbitrary $f$ is open. Our goal is to provide a suitable framework to resolve this problem and I will present some recent results in this direction. The key is a new (to the best of our knowledge) smoothing estimate for the heat semigroup between two arbitrary Orlicz spaces. Existence then follows familiar lines via monotonicity or contraction mapping arguments. Global solutions are also presented under additional assumptions. This work is part of a collaborative project with Prof Kazuhiro Ishige, Dr Yohei Fujishima and Dr Kotaro Hisa.
[ 参考URL ]We consider the local well-posedness of semilinear heat equations in Orlicz spaces, the latter prescribed via a Young function $\Phi$. Many existence-uniqueness results exist in the literature for power-like or exponential-like nonlinearities $f$, where the natural setting is an Orlicz space of corresponding type; i.e. if $f$ is power-like then $\Phi$ is power-like (Lebesgue space), if $f$ is exponential-like then $\Phi$ is exponential-like. However, the general problem of prescribing a suitable $\Phi$ for a given, otherwise arbitrary $f$ is open. Our goal is to provide a suitable framework to resolve this problem and I will present some recent results in this direction. The key is a new (to the best of our knowledge) smoothing estimate for the heat semigroup between two arbitrary Orlicz spaces. Existence then follows familiar lines via monotonicity or contraction mapping arguments. Global solutions are also presented under additional assumptions. This work is part of a collaborative project with Prof Kazuhiro Ishige, Dr Yohei Fujishima and Dr Kotaro Hisa.
https://forms.gle/ZEyVso6wa9QpNfxH7
2024年05月15日(水)
数値解析セミナー
16:30-18:00 数理科学研究科棟(駒場) 002号室
ハイブリッド開催です。参加の詳細は参考URLをご覧ください。
榊原航也 氏 (金沢大学理工研究域)
TBA (Japanese)
[ 参考URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
ハイブリッド開催です。参加の詳細は参考URLをご覧ください。
榊原航也 氏 (金沢大学理工研究域)
TBA (Japanese)
[ 参考URL ]
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
2024年05月20日(月)
複素解析幾何セミナー
10:50-12:20 数理科学研究科棟(駒場) 128号室
いつもより20分遅れて開始します。
孫 立杰 氏 (山口大学)
Kähler metrics in the Siegel domain (Japanese)
https://forms.gle/gTP8qNZwPyQyxjTj8
いつもより20分遅れて開始します。
孫 立杰 氏 (山口大学)
Kähler metrics in the Siegel domain (Japanese)
[ 講演概要 ]
The Siegel domain is endowed with an intrinsic Kähler structure, making it an exemplary model for the complex hyperbolic plane. Its boundary, characterized as the one-point compactification of the Heisenberg group, plays an important role in studying the geometry of the Siegel domain. In this talk, using the CR structure of the Heisenberg group we introduce a variety of Kähler structures within the Siegel domain. We conclude by demonstrating that all these metrics are PCR-Kähler equivalent, that is, essentially the same when confined to the CR structure. This talk is based on a joint work with Ioannis Platis and Joonhyung Kim.
[ 参考URL ]The Siegel domain is endowed with an intrinsic Kähler structure, making it an exemplary model for the complex hyperbolic plane. Its boundary, characterized as the one-point compactification of the Heisenberg group, plays an important role in studying the geometry of the Siegel domain. In this talk, using the CR structure of the Heisenberg group we introduce a variety of Kähler structures within the Siegel domain. We conclude by demonstrating that all these metrics are PCR-Kähler equivalent, that is, essentially the same when confined to the CR structure. This talk is based on a joint work with Ioannis Platis and Joonhyung Kim.
https://forms.gle/gTP8qNZwPyQyxjTj8
2024年05月27日(月)
複素解析幾何セミナー
10:30-12:00 数理科学研究科棟(駒場) 128号室
丸亀 泰二 氏 (電気通信大学)
TBA (Japanese)
https://forms.gle/gTP8qNZwPyQyxjTj8
丸亀 泰二 氏 (電気通信大学)
TBA (Japanese)
[ 講演概要 ]
TBA
[ 参考URL ]TBA
https://forms.gle/gTP8qNZwPyQyxjTj8
2024年05月29日(水)
数値解析セミナー
16:30-18:00 数理科学研究科棟(駒場) 002号室
ハイブリッド開催です。参加の詳細は参考URLをご覧ください。
早川知志 氏 (ソニーグループ株式会社)
ランダム凸包とカーネル求積 (Japanese)
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
ハイブリッド開催です。参加の詳細は参考URLをご覧ください。
早川知志 氏 (ソニーグループ株式会社)
ランダム凸包とカーネル求積 (Japanese)
[ 講演概要 ]
確率測度の離散近似の代表例として、古典的には低次モーメントのマッチングによるcubature（立体求積）がある。これは一般の空間においても有限個の可積分関数の積分値を保つような離散化として導入でき、ランダムサンプリングによるナイーブな構成が考えられる。講演の前半では、この確率的構成の成功確率を定式化したものとして、ランダム凸包が空間上の点を含む確率についてのバウンドを与える。後半ではさらに、この一般化cubatureの問題が（被積分関数のクラスとして再生核ヒルベルト空間を想定する）カーネル求積問題に実用的なアルゴリズムとともに応用できることをみる。
講演内容は次の学位論文にもとづく：
https://ora.ox.ac.uk/objects/uuid:15008016-2418-4c9a-a2f7-c9515a0657b1
[ 参考URL ]確率測度の離散近似の代表例として、古典的には低次モーメントのマッチングによるcubature（立体求積）がある。これは一般の空間においても有限個の可積分関数の積分値を保つような離散化として導入でき、ランダムサンプリングによるナイーブな構成が考えられる。講演の前半では、この確率的構成の成功確率を定式化したものとして、ランダム凸包が空間上の点を含む確率についてのバウンドを与える。後半ではさらに、この一般化cubatureの問題が（被積分関数のクラスとして再生核ヒルベルト空間を想定する）カーネル求積問題に実用的なアルゴリズムとともに応用できることをみる。
講演内容は次の学位論文にもとづく：
https://ora.ox.ac.uk/objects/uuid:15008016-2418-4c9a-a2f7-c9515a0657b1
https://sites.google.com/g.ecc.u-tokyo.ac.jp/utnas-bulletin-board/
