過去の記録

過去の記録 ~02/23本日 02/24 | 今後の予定 02/25~

2016年04月04日(月)

数値解析セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
Eric Chung 氏 (Chinese University of Hong Kong)
Staggered discontinuous Galerkin methods for the incompressible Navier-Stokes equations (English)
[ 講演概要 ]
In this talk, we present a staggered discontinuous Galerkin method for the approximation of the incompressible Navier-Stokes equations. Our new method combines the advantages of discontinuous Galerkin methods and staggered meshes, and results in many good properties, namely local and global conservations, optimal convergence and superconvergence through the use of a local postprocessing technique. Another key feature is that our method provides a skew-symmetric discretization of the convection term, with the aim of giving a better conservation property compared with existing discretizations. We also analyze the stability and convergence of the method. In addition, we will present some numerical results to show the performance of the proposed method.

2016年03月29日(火)

代数学コロキウム

17:30-18:30   数理科学研究科棟(駒場) 002号室
曜日・部屋がいつもと異なりますのでご注意ください.
Matthew Morrow 氏 (Universität Bonn)
Motivic cohomology of formal schemes in characteristic p
(English)
[ 講演概要 ]
The logarithmic Hodge-Witt sheaves of Illusie, Milne, Kato, et al. of a smooth variety in characteristic p provide a concrete realisation of its p-adic motivic cohomology, thanks to results of Geisser-Levine and Bloch-Kato-Gabber which link them to algebraic K-theory. I will explain an analogous theory for formal schemes, as well as applications to algebraic cycles, such as a weak Lefschetz theorem for formal Chow groups.

(本講演は「東京北京パリ数論幾何セミナー」として, インターネットによる東大数理, Morningside Center of MathematicsとIHESの双方向同時中継で行います.)

2016年03月22日(火)

談話会・数理科学講演会

16:50-17:50   数理科学研究科棟(駒場) 大講義室号室
お茶会の場所はいつもと異なる、大講義室前ホワイエです。
石井志保子 氏 (東京大学大学院数理科学研究科)
Singularities and Jet schemes (JAPANESE)
[ 講演概要 ]
特異点を記述するためにいろいろな不変数が考えられていますがその中で比較的最近登場した Mather-Jacobian discrepancy と,特異点の上の jet schemes の関係を先ず紹介します.
この関係は多様体の基礎体の標数が0の場合には,このdiscrepancy 導入当初から知られており,
正標数の場合には最近証明されました.
これにより,特異点解消の存在がまだ証明されていない正標数の体上の特異点についても jet schemes を用いて
研究が進むことが期待されます.
本講演では,低次元の場合にそれがうまく機能することを紹介し,任意次元で機能するための課題を紹介します.

[ 講演参考URL ]
http://faculty.ms.u-tokyo.ac.jp/~shihoko/

FMSPレクチャーズ

10:00-11:00   数理科学研究科棟(駒場) 118号室
Fatiha Alabau 氏 (Université de Lorraine)
Control and stabilization of degenerate wave equations (ENGLISH)
[ 講演概要 ]
The control of degenerate PDE's arise in many applications such as cloaking, climatology, population genetics, and vision.
For such models, the diffusion operator degenerates on some subset of the spatial domain. We present some recent results on observability, control and stabilization of these equations.
This is a joint work with Piermarco Cannarsa (University di Roma Tor Vergata, Italy) and G\"unter Leugering (Friedrich-Alexander-Universit\"at Erlangen-N\"urnberg, Erlangen, Germany).
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Alabau.pdf

FMSPレクチャーズ

11:00-12:00   数理科学研究科棟(駒場) 118号室
Mourad Bellassoued 氏 (Université de Tunis El Manar)
Stable determination of coefficients in the dynamical Schrödinger equation in a magnetic field (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Bellassoued.pdf

2016年03月19日(土)

FMSPレクチャーズ

11:00-12:00   数理科学研究科棟(駒場) 370号室
Oleg Emanouilov 氏 (Colorado State Univ.)
About the Landis conjecture (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Emanouilov160319.pdf

2016年03月18日(金)

FMSPレクチャーズ

14:30-15:30   数理科学研究科棟(駒場) 118号室
Piermarco Cannarsa 氏 (Università degli Studi di Roma Tor Vergata)
Control of degenerate parabolic equations: old and new (ENGLISH)
[ 講演概要 ]
This talk will survey the main results obtained in the last fifteen years or so for the null controllability of degenerate parabolic operators.
We shall describe the state of the art for operators which degenerate at the boundary as well as for certain classes of interior degeneracy of hypoelliptic type.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Cannarsa.pdf

2016年03月16日(水)

PDE実解析研究会

16:00-17:00   数理科学研究科棟(駒場) 056号室
通常の曜日、時刻と異なります。
Boris Khesin 氏 (University of Toronto)
Fluids, vortex membranes, and skew-mean-curvature flows (English)
[ 講演概要 ]
We show that an approximation of the hydrodynamical Euler equation describes the skew-mean-curvature flow on vortex membranes in any dimension. This generalizes the classical binormal, or vortex filament, equation in 3D. We present a Hamiltonian framework for dynamics of higher-dimensional vortex filaments and vortex sheets as singular 2-forms (Green currents) with support of codimensions 2 and 1, respectively.

2016年03月11日(金)

作用素環セミナー

16:45-18:15   数理科学研究科棟(駒場) 118号室
Bas Jordans 氏 (Univ. Oslo)
Convergence to the boundary for random walks on discrete quantum groups
(English)

2016年03月08日(火)

作用素環セミナー

16:45-18:15   数理科学研究科棟(駒場) 118号室
Roberto Longo 氏 (ローマ大学)
Equilibrium and non-equilibrium states in Conformal Field Theory (英語)

2016年02月22日(月)

FMSPレクチャーズ

17:00-18:00   数理科学研究科棟(駒場) 118号室
Michel Cristofol 氏 (Aix-Marseille Univ.)
Inverse problems for parabolic operators : comparison of three different approaches (ENGLISH)
[ 講演概要 ]
Basing my talk around a toy problem : reconstruction of the potential for a linear parabolic problem, I will recall the two main classical following methods : Dirichlet to Neumann map and Carleman estimates. Then I will present a different and recent approach based on pointwise observations and I will underline some points to be improved for each method. Then, I will finish my talk by a review of some results related to this technic of pointwise observations.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Cristofol.pdf

2016年02月19日(金)

FMSPレクチャーズ

10:30-11:30   数理科学研究科棟(駒場) 118号室
Olivier Poisson 氏 (Aix-Marseille University)
Recovering time-dependent inclusion in heat conductive bodies by a dynamical probe method (ENGLISH)
[ 講演概要 ]
Many articles solve a version of the Calder'on inverse problem for the heat equation. The biggest part of them assume that the unknown conductivity do not depend on time t. But they are very few results concerning the time de- pendent situation, and they are based on the computation of an ansatz for the parabolic equation:
- A reconstruction method of an unknown moving inclusion by a dynamical probe method was performed by Daido-Kang-Nakamura in 2007, but it works for the one dimensional spatial space only,
- An energy estimate for x-multidimensional convex inclusions.
In the talk I will present a dynamical probe method based on special fundamental solutions of the heat equation and basic inequalities :
this approach is very close to the probe method for the elliptic Calderon inverse problem, and does not require regularity of the inclusion.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Poisson.pdf

2016年02月18日(木)

FMSPレクチャーズ

10:00-11:00   数理科学研究科棟(駒場) 002号室
This lecture will be given as part of “Workshop on L^2 Extension Theorems”.
Dror Varolin 氏 (Stony Brook)
L^2 Extension and its applications: A survey (3) (ENGLISH)
[ 講演概要 ]
We discuss certain aspects of the theory of L^2 extension, going back to the famous and fundamental work of Ohsawa and Takegoshi, and even further back to work of Donnelly and Fefferman.
The first of three lectures will recall a number of L^2 extension theorems, to some extent following an incomplete history (as I see it), and ending with a sketch of a proof of one of these theorems.
The second lecture will discuss a number of my favorite applications of L^2 extension, from Bergman kernels to deformation invariance of plurigenera.
The third lecture will discuss a new proof of the extension theorem, due to Berndtsson and Lempert. The key tool is a theorem of Berndtsson on the positivity of direct images, which we will review. Berndtsson's theorem permits the introduction of degeneration techniques, whose surprising application to L^2 extension represents one of the most beautiful and fundamental recent breakthroughs in the subject.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Varolin.pdf

FMSPレクチャーズ

10:30-11:30   数理科学研究科棟(駒場) 118号室
Michel Cristofol 氏 (Aix-Marseille Univ.)
Inverse boundary value problem for a hyperbolic equation in an infinite guide (ENGLISH)
[ 講演概要 ]
We consider the multidimensional inverse problem of determining the conductivity coefficient of a hyperbolic equation in an infinite cylindrical domain, from a single boundary observation of the solution. We prove Holder stability with the aid of a Carleman estimate specially designed for hyperbolic waveguides. I will provide numerical simulations in multiple backgrounds.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Cristofol.pdf

2016年02月17日(水)

FMSPレクチャーズ

10:00-11:00   数理科学研究科棟(駒場) 002号室
This lecture will be given as part of “Workshop on L^2 Extension Theorems”.
Dror Varolin 氏 (Stony Brook)
L^2 Extension and its applications: A survey (2) (ENGLISH)
[ 講演概要 ]
We discuss certain aspects of the theory of L^2 extension, going back to the famous and fundamental work of Ohsawa and Takegoshi, and even further back to work of Donnelly and Fefferman.
The first of three lectures will recall a number of L^2 extension theorems, to some extent following an incomplete history (as I see it), and ending with a sketch of a proof of one of these theorems.
The second lecture will discuss a number of my favorite applications of L^2 extension, from Bergman kernels to deformation invariance of plurigenera.
The third lecture will discuss a new proof of the extension theorem, due to Berndtsson and Lempert. The key tool is a theorem of Berndtsson on the positivity of direct images, which we will review. Berndtsson's theorem permits the introduction of degeneration techniques, whose surprising application to L^2 extension represents one of the most beautiful and fundamental recent breakthroughs in the subject.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Varolin.pdf

2016年02月16日(火)

トポロジー火曜セミナー

17:00-18:30   数理科学研究科棟(駒場) 056号室
Tea : Common Room 16:30 -- 17:00
Luc Menichi 氏 (University of Angers)
String Topology, Euler Class and TNCZ free loop fibrations (ENGLISH)
[ 講演概要 ]
Let $M$ be a connected, closed oriented manifold.
Chas and Sullivan have defined a loop product and a loop coproduct on
$H_*(LM;¥mathbb{F})$, the homology of the
free loops on $M$ with coefficients in the field $¥mathbb{F}$.
By studying this loop coproduct, I will show that if the free loop
fibration
$¥Omega M¥buildrel{i}¥over¥hookrightarrow
LM¥buildrel{ev}¥over¥twoheadrightarrow M$
is homologically trivial, i.e. $i^*:H^*(LM;¥mathbb{F})¥twoheadrightarrow
H^*(¥Omega M;¥mathbb{F})$ is onto,
then the Euler characteristic of $M$ is divisible by the characteristic
of the field $¥mathbb{F}$
(or $M$ is a point).

FMSPレクチャーズ

10:00-11:00   数理科学研究科棟(駒場) 002号室
This lecture will be given as part of “Workshop on L^2 Extension Theorems”.
Dror Varolin 氏 (Stony Brook)
L^2 Extension and its applications: A survey (1) (ENGLISH)
[ 講演概要 ]
We discuss certain aspects of the theory of L^2 extension, going back to the famous and fundamental work of Ohsawa and Takegoshi, and even further back to work of Donnelly and Fefferman.
The first of three lectures will recall a number of L^2 extension theorems, to some extent following an incomplete history (as I see it), and ending with a sketch of a proof of one of these theorems.
The second lecture will discuss a number of my favorite applications of L^2 extension, from Bergman kernels to deformation invariance of plurigenera.
The third lecture will discuss a new proof of the extension theorem, due to Berndtsson and Lempert. The key tool is a theorem of Berndtsson on the positivity of direct images, which we will review. Berndtsson's theorem permits the introduction of degeneration techniques, whose surprising application to L^2 extension represents one of the most beautiful and fundamental recent breakthroughs in the subject.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Varolin.pdf

FMSPレクチャーズ

16:00-17:00   数理科学研究科棟(駒場) 270号室
Patricia Gaitan 氏 (Aix-Marseille University)
Inverse Problem for an Hyperbolic-Parabolic System and Perspectives (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Gaitan160216.pdf

2016年02月15日(月)

FMSPレクチャーズ

17:00-18:00   数理科学研究科棟(駒場) 118号室
Patricia Gaitan 氏 (Aix-Marseille University)
Probing for inclusions for heat conductive bodies time independent and time dependent cases (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Gaitan.pdf

2016年02月08日(月)

東京確率論セミナー

16:50-18:20   数理科学研究科棟(駒場) 128号室
長田 博文 氏 (九州大学大学院数理学研究院)
Dynamical rigidity of stochastic Coulomb systems
[ 講演概要 ]
Ginibre点過程の劣拡散性の証明を中心に話をします.

東京無限可積分系セミナー

13:30-15:00   数理科学研究科棟(駒場) 002号室
Vincent Pasquier 氏 (IPhT Saclay)
q-Bosons, Toda lattice and Baxter Q-Operator (ENGLISH)
[ 講演概要 ]
I will use the Pieri rules of the Hall Littlewood polynomials to construct some
lattice models, namely the q-Boson model and the Toda Lattice Q matrix.
I will identify the semi infinite chain transfer matrix of these models with well known
half vertex operators. Finally, I will explain how the Gaudin determinant appears in the evaluation
of the semi infine chain scalar products for an arbitrary spin and is related to the Macdonald polynomials.

2016年02月01日(月)

東京確率論セミナー

16:50-18:20   数理科学研究科棟(駒場) 270号室
部屋がいつもと異なります.ご注意ください.
曽我 幸平 氏 (慶應義塾大学理工学部)
数値粘性の確率論的特徴付けとその応用
[ 講演概要 ]
非線形双曲型偏微分方程式の数値解析において、数値粘性と呼ばれるある種の拡散効果が観察される。本講演では、この効果が非一様ランダムウォークで特徴付けられることを見る。これはラプラシアンが有する拡散効果の確率論的特徴付けを想起させる。さらにこの方法によって、差分法の収束が大数の法則によって見通しよく議論できることを見る。従来の数値解析の枠組みでは得られなかった差分法の安定性・収束・誤差評価などに関する新たな結果も紹介する。時間が許せば、弱KAM理論と呼ばれる力学系理論の数値解析への応用についても触れたい。

2016年01月29日(金)

博士論文発表会

9:15-10:30   数理科学研究科棟(駒場) 118号室
北川 宜稔 氏 (東京大学大学院数理科学研究科)
Algebraic structure on the space of intertwining operators(絡作用素の空間上の代数構造) (JAPANESE)

博士論文発表会

10:45-12:00   数理科学研究科棟(駒場) 118号室
中濱 良祐 氏 (東京大学大学院数理科学研究科)
Some topics on analysis of holomorphic discrete series representations(正則離散系列表現の解析に関するいくつかの話題) (JAPANESE)

博士論文発表会

12:45-14:00   数理科学研究科棟(駒場) 118号室
古川 遼 氏 (東京大学大学院数理科学研究科)
On codimension two contact embeddings in the standard spheres(標準接触球面への余次元2の接触埋め込みについて)

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