過去の記録

過去の記録 ~11/11本日 11/12 | 今後の予定 11/13~

東京無限可積分系セミナー

15:00-16:00   数理科学研究科棟(駒場) 117号室
土谷洋平 氏 (東大数理)
積分変換の項を持つソリトン方程式とその解の構造について
[ 講演概要 ]
ソリトン方程式の中には特異積分変換の項を持つIntermediate long wave, Benjamin-Ono, intermediate nonlinear Schr\\"{o}dinger などの方程式がある。これらの方程式は,適当な条件の下で微差分系(関数微分方程式)に書き換えると佐藤理論の枠組みで捉えることができるようになる。このような方法を中心に現在分かっていることと問題点を紹介したい。

2006年11月17日(金)

統計数学セミナー

15:00-16:10   数理科学研究科棟(駒場) 118号室
清水 泰隆 氏 (大阪大学大学院基礎工学研究科)
Functional estimation of L'evy measure for jump-type processes
[ 講演概要 ]
Recently, stochastic processes with Poissonian jumps are frequently used in finance and insurance. In their applications, it often becomes important to estimate some functionals of integral types with respect to L'evy measures. In this talk, we propose a nonparametric estimator of their functionals based on both continuous and discrete observations. If time permits, we shall also mention the application to the mathematical insurance, in particular, the estimates of ruin probabilities for genelarized risk processes.
[ 講演参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/13.html

2006年11月16日(木)

講演会

16:30-18:00   数理科学研究科棟(駒場) 118号室
Pierre Berthelot 氏 (Rennes大学)
Crystalline complexes and D-modules

応用解析セミナー

16:00-17:30   数理科学研究科棟(駒場) 056号室
奈良 光紀 氏 (東京工業大学)
The large time behavior of graphical surfaces in the mean curvature flow
[ 講演概要 ]
We are interested in the large time behavior of a surface in the whole space moving by the mean curvature flow. Studying the Cauchy problem on $R^{N}$, we deal with moving surfaces represented by entire graphs. We focus on the case of $N=1$ and the case of $N\\geq2$ with radially symmetric surfaces. We show that the solution converges uniformly to the solution of the Cauchy problem of the heat equation, if the initial value is bounded. Our results are based on the decay estimates for the derivatives of the solution. This is a joint work with Prof. Masaharu Taniguchi of Tokyo Institute of Technology.

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 126号室
戸松玲治 氏 (東大数理)
商型右余イデアルの特徴づけとポワソン境界の分類

2006年11月15日(水)

講演会

16:30-18:00   数理科学研究科棟(駒場) 117号室
Pierre Berthelot 氏 (Rennes大学)
Crystalline complexes and D-modules

数理ファイナンスセミナー

17:30-19:00   数理科学研究科棟(駒場) 118号室
塚原 英敦 氏 (成城大)
歪みリスク尺度の1-パラメータ族とその応用

2006年11月14日(火)

トポロジー火曜セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
Tea: 16:00 - 16:30 コモンルーム
高瀬将道 氏 (信州大学理学部)
High-codimensional knots spun about manifolds
[ 講演概要 ]
The spinning describes several methods of constructing higher-dimensional knots from lower-dimensional knots.
The original spinning (Emil Artin, 1925) has been generalized in various ways. Using one of the most generalized forms of spinning, called "deform-spinning about a submanifold" (Dennis Roseman, 1989), we analyze in a geometric way Haefliger's smoothly knotted (4k-1)-spheres in the 6k-sphere.

2006年11月13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
小野 肇 氏 (東京工業大学)
Sasaki-Futaki invariant and existence of Einstein metrics on toric Sasaki manifolds

代数幾何学セミナー

16:30-18:00   数理科学研究科棟(駒場) 126号室
青木昌雄 氏 (京大数理研)
Hom stacks and Picard stacks

2006年11月10日(金)

東京幾何セミナー

16:00-17:30   数理科学研究科棟(駒場) 056号室
中島啓 氏 (京都大学大学院理学研究科)
箙多様体のベッチ数の計算
[ 講演概要 ]
箙多様体の S^1 作用に関する固定点は, 次数付き箙多様体と呼ばれる. そのベッチ数の母関数は, 量子ループ代数の q-指標の t-類似と呼ばれ, 表現論的に大切な対象である. このベッチ数を, 仮想ホッジ多項式と, 箙多様体の stratified グラスマン束の構造を用いて計算するアルゴリズムを紹介する. 時間があれば, 大型計算機による計算結果についても紹介する.

トポロジー火曜セミナー

17:40-19:00   数理科学研究科棟(駒場) 118号室
樋上和弘 氏 (東京大学大学院理学系研究科 物理)
WRT invariant for Seifert manifolds and modular forms
[ 講演概要 ]
We study the SU(2) Witten-Reshetikhin-Turaev invariant for Seifert manifold. We disuss a relationship with the Eichler integral of half-integral modular form and Ramanujan mock theta functions.

2006年11月09日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 126号室
水田有一 氏 (東大数理)
Operator-algebraic superrigidity for SL_n(Z) II(Bekkaの論文の紹介)

講演会

16:20-17:50   数理科学研究科棟(駒場) 123号室
S. Bloch 氏 (シカゴ大学)
<連続講演> Graphs and motives

2006年11月08日(水)

諸分野のための数学研究会

10:30-11:30   数理科学研究科棟(駒場) 056号室
Fredric Flin 氏 (Hokkaido University)
Crystal growth in dry deposited snow: experiment, theoretical modeling and simulation
[ 講演概要 ]
Snow, from its fall until its full melting, undergoes transformations of its microstructure with time. This process, named “metamorphism”, drastically influences its physical, thermal and mechanical properties and is of great interest in snow and ice sciences.
The recent possibility of acquiring 3D images of small snow samples opens new opportunities for investigating snow in details. For this purpose, we developed specific algorithms in order to extract the relevant geometrical and physical parameters from the imaged samples (e.g. normal and curvature fields, specific surface area). We then used these estimators to develop 3D models that simulate the time-lapse transformations of snow directly from an experimentally observed microstructure. These models, which can be checked with experiments in cold room, offer new outlooks for the study of snow metamorphism.
[ 講演参考URL ]
http://coe.math.sci.hokudai.ac.jp/sympo/various/index.html

講演会

16:20-17:50   数理科学研究科棟(駒場) 123号室
S. Bloch 氏 (シカゴ大学)
<連続講演> Graphs and motives

東京幾何セミナー

14:40-18:00   数理科学研究科棟(駒場) 056号室
梶原 健 氏 (横浜国立大学大学院工学研究院応用数学) 14:40-16:10
代数多様体の退化とトロピカル幾何
[ 講演概要 ]
トロピカル幾何について説明しながら,多様体の退化等との関係や既知の応用について,簡単に紹介します.また,具体的にトロピカル超曲面で記述される退化として,射影トーリック多様体の退化について説明します.ここで現れる退化トーリック多様体は,Alexeev 氏がアーベル多様体のモジュライ空間のコンパクト化の研究において導入した,安定トーリック多様体です.
西納 武男 氏 (京都大学理学研究科数学教室) 16:30-18:00
Counting problem in tropical geometry
[ 講演概要 ]
この講演ではここ数年進展したトロピカル曲線を用いたトーリック多様体上の正則曲線の数え上げについて解説したいと思います.
はじめにトロピカル曲線と正則曲線の関係について,正則曲線のアメーバを介して(Target spaceが複素2次元の場合に)直感的な説明を試みます.トロピカル曲線は実1次元のグラフ状の集合ですが,複素構造のような幾何学的対象の退化を考えると自然に現れます.その考えに基づき,トロピカル曲線がトーリック多様体の退化と自然に関わることと,その事実の数え上げへの応用についてお話ししたいと思います.時間があればディスクの数え上げの場合について,閉曲線の場合との関係などにも触れたいと思います.

統計数学セミナー

16:20-17:30   数理科学研究科棟(駒場) 128号室
蛭川 潤一 氏 (早稲田大学)
LAN Theorem for Non-Gaussian Locally Stationary Processes and Their Discriminant and Cluster Analyses
[ 講演概要 ]
This talk is concerned with asymptotic inference for non-Gaussian locally stationary processes. Lucien LeCam established the most important and sophisticated foundation of the general statistical asymptotic theory. He introduced the concept of local asymptotic normality (LAN) for the likelihood ratio of general statistical models. Once LAN is proved, the asymptotic optimality of estimators and tests is described in terms of the LAN property. The techniques of statistical inference for stationary time series have been well established. However, stationary time series model is not plausible to describe the real world. One of the difficult problem when we deal with nonstationary processes is how to set up an adequate model. Otherwise, the observation in the future will bring no information for the present structure. Recently, Dahalhaus has proposed an important class of nonstationary processes, called locally stationary processes. Locally stationary processes have the time varying densities whose spectral structures smoothly change in time. In this talk, we first show the LAN results for locally stationary processes under the assumption of the non-Gaussianity. Then, we apply the LAN theorem to estimation and testing theory, non-Gaussian robustness and adaptive estimation. Our LAN theorem elucidates various non-Gaussian asymptotics. Next, we develop asymptotic theory for discriminant and cluster analyses of non-Gaussian locally stationary processes. We discuss about non-Gaussian robustness of our classification statistic. Furthermore, we execute the clustering of stock returns in Tokyo Stock Exchanges. Consequently, we observe that the clustering results well extract features of relationships among companies.
[ 講演参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/13.html

2006年11月07日(火)

講演会

16:20-17:50   数理科学研究科棟(駒場) 123号室
11月7日(火)-11月9日(木)の連続講演です.
担当者: 斎藤 毅

S. Bloch 氏 (シカゴ大学)
<連続講演> Graphs and motives

2006年11月06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
Mihai Paun 氏 (Université Henri Poincaré Nancy)
On the extension of twisted pluricanonical forms

2006年11月02日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 126号室
水田有一 氏 (東大数理)
Operator-algebraic superrigidity for SL_n(Z) I(Bekkaの論文の紹介)

応用解析セミナー

16:00-17:30   数理科学研究科棟(駒場) 056号室
Messoud Efendiev 氏 (ミュンヘン工科大学)
On attractor of Swift-Hohenberg equation in unbounded domain and its Kolmogorov entropy
[ 講演概要 ]
The main objective of the talk is to give a description of the large-time behaviour of solutions of the Swift-Hohenberg equation in unbounded domain.This will be done in terms of the global attractor. Here we encounter serious difficulties due to the lack of compactness of the embedding theorems and the interplay between the different topologies will play crucial role.We prove the existence of the global attractor and show that the restriction of the attractor to any bounded sets has an infinite fractal dimension and present sharp estimate for its Kolmogorov entropy.Spatio-temporal chaotic dynamics on the attractor will also be discussed.

2006年11月01日(水)

代数学コロキウム

16:30-18:45   数理科学研究科棟(駒場) 117号室
2講演です
G.Bayarmagnai 氏 (東大数理) 16:30-17:30
Essential dimension of some finite group schemes
Jacques Tilouine 氏 (パリ北大学) 17:45-18:45
Overconvergent Siegel modular forms
[ 講演概要 ]
We recall what is known and what is conjectured on p-adic families of overconvergent Siegel modular forms. We show how this relates to a Fontaine-Mazur type conjecture on the classicality of certain overconvergent Siegel forms of genus 2. We explain few results known in this direction.

統計数学セミナー

15:00-16:10   数理科学研究科棟(駒場) 128号室
Ilia NEGRI 氏 (Department of Management and Information Technology, University of Bergamo, Italy)
Some problems related to the estimation of the invariant measure of an ergodic diffusion.
[ 講演概要 ]
We consider a one dimensional ergodic diffusion process solution of a stochastic differential equation. We suppose that the diffusion coefficient is known whereas the drift coefficient $S$ is unknown. Our interest is the invariant measure of the process denoted as $\\mu $. We denote by $f_S$ and $F_S$ the invariant density and the invariant distribution function of $\\mu$ respectively. We present the problems of finding efficient estimators when we observe the trajectory of the diffusion in continuos time over $[0,T]$ and we study asymptotic properties of the estimators when $T$ goes to infinity.
[ 講演参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2006/12.html

PDE実解析研究会

10:30-11:30   数理科学研究科棟(駒場) 128号室
Tan Yongji 氏 (School of Mathematical Science, Fudan University )
A case study in petroleum industry: Mathematical modeling and numerical simulation in spontaneous potential well-logging
[ 講演概要 ]
Spontaneous well-logging is an important technique in petroleum exploitation. The potential field is of strong discontinuity on the interface since the spontaneous potential differences. It causes difficulty in mathematical analysis and numerical computing.

New mathematical model and numerical method is designed to overcome the difficulty and good results is obtained.
[ 講演参考URL ]
http://coe.math.sci.hokudai.ac.jp/sympo/pde_ra/index.html

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