過去の記録

過去の記録 ~09/27本日 09/28 | 今後の予定 09/29~

2009年05月14日(木)

応用解析セミナー

16:00-17:30   数理科学研究科棟(駒場) 002号室
東海林 まゆみ 氏 (日本女子大学・理学部・数物科学科)
Particle trajectories around a running cylinder in Brinkman's porous-media flow
[ 講演概要 ]
Motion of fluid particles provides us with interesting problems of dynamical
systems. We consider here the movement of particles around a running cylinder.
Classically J. C. Maxwell (1870) considered the problem in irrotational flow of
inviscid fluid. He showed that the complete solution is given by the elliptic
functions and the trajectory forms one of the elastica curves. C. Darwin ('53)
considered a similar problem for a moving sphere. In this case, the solution
cannot be written in terms of elliptic functions but can be expressed by a
simple definite integral.
We consider a similar problem in Brinkman's porous-media flow which is proposed
by Brinkman ('49). Our numerical examinations reveals some new interesting
features of the particle trajectories which are not observed in the case of
irrotational flow. We will report them.

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
Raphael Ponge 氏 (東大数理)
Noncommutative geometry and lower dimensional volumes in Riemannian and CR geometry

数理人口学・数理生物学セミナー

16:00-17:30   数理科学研究科棟(駒場) 123号室
岩見真吾 氏 (静岡大学創造科学技術大学院)
AIDSワクチン開発への理論的介入-SHIV感染実験と数理モデル-
[ 講演概要 ]
慢性感染症であるという特性を有するHIV感染症の拡大を阻止するためには、予防・治療AIDSワクチンの開発が不可欠である。しかし、1998年にヒトでは初めての国際的な臨床試験が始まったバックスジェン社のAIDSワクチンは、2003年に失敗だと発表された。また、2004年メルク社の最も有望だったワクチン候補も大規模な臨床試験にまで進んだが、効果がないどころか悪影響がある可能性が判明し、2007年に打ち切られた。HIV単離からすでに25年たった今でも、まだ効果的なワクチンは開発されていない。このように、HIVに対して従来のワクチン製造法では有効なワクチンを作れなかったとなれば、何かこれまでとは違う革新的な治療戦略が必要である。そこで、本研究では、HIVとその体内での振る舞いに関する基本的な疑問と取り組み、HIVを無力化する新しい方法を見つけ出すこと目指す。まず身体に備わった免疫応答が通常どのように機能するのかを知るために、HIVとよく似たSHIVの感染実験と数理モデルを用いて、SHIVの性状、病原性、免疫反応性を明らかにする。今回のセミナーでは、培養細胞での実験データから推定可能であるウイルスの増殖率と感染力によって特徴づけられるSHIVの病原性評価理論を紹介する。

2009年05月13日(水)

代数学コロキウム

16:30-18:45   数理科学研究科棟(駒場) 056号室
大久保 俊 氏 (東京大学大学院数理科学研究科) 16:30-17:30
剰余体が非完全な場合のB_dR^+のGalois理論
斎藤 秀司 氏 (東京大学大学院数理科学研究科) 17:45-18:45
A counterexample of Bloch-Kato conjecture over a local field and infinite torsion in algebraic cycles of codimension two

2009年05月12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
松田 能文 氏 (東京大学大学院数理科学研究科)
Discrete subgroups of the group of circle diffeomorphisms
[ 講演概要 ]
Typical examples of discrete subgroups of the group of circle diffeomorphisms
are Fuchsian groups.
In this talk, we construct discrete subgroups of the group of
orientation-preserving
real analytic cirlcle diffeomorphisms
which are not topologically conjugate to finite coverings of Fuchsian groups.

統計数学セミナー

16:20-17:30   数理科学研究科棟(駒場) 126号室
塩濱 敬之 氏 (東京理科大学, 工学部)
Asymptitically efficient estimation of multiple change points in GARCH types models
[ 講演概要 ]
Instability of volatility parameters in GARCH models in an important issue for analyzing financial time series. In this paper we investigate the asymptotic theory for multiple change point estimators of GARCH$(p,q)$ models. When the parameters of a GARCH models have changed within an observed realization, two types estimators, Maximum likelihood estimator (MLE) and Bayesian estimator (BE), are proposed. Then we derive the asymptotic distributions for these estimators. The MLE and BE have different limit laws, and the BE is asymptotically efficient. Monte Carlo studies on the finite sample behaviors are conducted. Applications to Nikkei 225 index are discussed.
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/03.html

2009年05月11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) 126号室
林本厚志 氏 (長野高専)
CR幾何学でのドラーム分解型定理

2009年05月07日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
見村万佐人 氏 (東大数理)
A fixed point property and the Kazhdan property of
$SL(n, \\mathbb{Z} [X_1, \\ldots , X_k])$ for Banach spaces

2009年04月30日(木)

応用解析セミナー

16:00-17:30   数理科学研究科棟(駒場) 002号室
池田 幸太 氏 (明治大 研究・知財戦略機構)
ギーラー・マインハルト方程式に対するシャドウ系おける多重スポットの不安定性
[ 講演概要 ]
生物の形態形成に関するモデル方程式である、ギーラー・マインハルト方程式に対するシャドウ系を考える。
この系にはスポットパターンと呼ばれる定常解が存在することが知られており、この解は、その値が非常に大きい点(スポット)を持つこととその近傍の外側では急激に値が減少することにより特徴付けされる。
実は、パラメータと領域を固定しても、単一のスポットだけからなるものや、2つ以上のスポットを持つ定常解、多重スポットが同時に存在しうるが、多重スポットは常に不安定であると予想されている。
本講演では、この予想を数学的に保証するために、多重スポットが適当な条件を満たせば不安定であることを示したい。

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 056号室
酒匂宏樹 氏 (東大数理)
Measure Equivalence Rigidity and Bi-exactness of Groups

2009年04月28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
平地 健吾 氏 (東京大学大学院数理科学研究科)
The ambient metric in conformal geometry
[ 講演概要 ]
In 1985, Charles Fefferman and Robin Graham gave a method for realizing a conformal manifold of dimension n as a submanifold of a Ricci-flat Lorentz metric on a manifold of dimension n+2, which is now called the ambient space. Using this correspondence, one can construct many examples of conformal invariants and conformally invariant operators. However, if n is even, their construction of the ambient space is obstructed at the jet of order n/2 and thereby the application of the ambient space was limited. In this talk, I'll recall basic ideas of the ambient space and then explain how to avoid the difficulty and go beyond the obstruction. This is a joint work with Robin Graham.

解析学火曜セミナー

16:30-18:00   数理科学研究科棟(駒場) 128号室
下村 明洋 氏 (首都大学東京)
非線型消散項を伴うシュレディンガー方程式の任意の大きさの初期データに対する解の漸近挙動(北直泰氏との共同研究)

2009年04月27日(月)

代数幾何学セミナー

15:30-18:00   数理科学研究科棟(駒場) 122号室
Prof. Alessandra Sarti 氏 (Universite de Poitier) 15:30-16:30
Automorphism groups of K3 surfaces
[ 講演概要 ]
I will present recent progress in the study of prime order automorphisms of K3 surfaces.
An automorphism is called (non-) symplectic if the induced
operation on the global nowhere vanishing holomorphic two form
is (non-) trivial. After a short survey on the topic, I will
describe the topological structure of the fixed locus, the
geometry of these K3 surfaces and their moduli spaces.

Prof. Samuel Boissier 氏 (Universite de Nice
) 17:00-18:00
The cohomological crepant resolution conjecture


[ 講演概要 ]
The cohomological crepant resolution conjecture is one
form of Ruan's conjecture concerning the relation between the
geometry of a quotient singularity X/G - where X is a smooth
complex variety and G a finite group of automorphisms - and the
geometry of a crepant resolution of singularities of X/G ; it
generalizes the classical McKay correspondence. Following the
examples of the Hilbert schemes of points on surfaces and the
weighted projective spaces, I will present some of the recents
developments of the subject.

2009年04月23日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 128号室
内藤克利 氏 (首都大)
Entire Cyclic Cohomology of Noncommutative 2-Tori

2009年04月22日(水)

PDE実解析研究会

10:30-11:30   数理科学研究科棟(駒場) 128号室
いつもとは会場が異なります。
Wilhelm Klingenberg 氏 (University of Durham)
From Codazzi-Mainardi to Cauchy-Riemann
[ 講演概要 ]
In joint work with Brendan Guilfoyle we established an upper bound for the winding number of the principal curvature foliation at any isolated umbilic of a surface in Euclidean three-space. In our talk, we will focus on the analytic core of the problem. Here is a model of the triaxial ellipsoid with its curvature foliation and one umbilic on the right.

東京幾何セミナー

14:45-18:00   数理科学研究科棟(駒場) 122号室
場所は東大数理(駒場)、東京工業大学(大岡山)のいずれかで行います。
詳細については、上記セミナーURLよりご確認下さい。
「今後の予定」欄には、東工大で行われるセミナーは表��

中田文憲 氏 (東京工業大学理工学研究科) 14:45-16:15
Einstein-Weyl structures on 3-dimensional Severi varieties
[ 講演概要 ]
The space of nodal curves on a projective surface is called a Severi variety.In this talk, we show that any Severi variety of nodal rational curves on a non-singular projective surface is always equipped with a natural Einstein-Weyl structure, if the space is 3-dimensional. This is a generalization of the Einstein-Weyl structure on the space of smooth rational curves on a complex surface, given by N. Hitchin in the context of twistor theory. We will explain some properties of the Einstein-Weyl spaces given by this method, and we will also show some examples of such Einstein-Weyl spaces. (This is a joint work with Nobuhiro Honda.)
Tamas Hausel 氏 (Oxford University) 16:30-18:00
Toric non-Abelian Hodge theory
[ 講演概要 ]
First we give an overview of the geometrical and topological aspects of the spaces in the non-Abelian Hodge theory of a curve and their connection with quiver varieties. Then by concentrating on toric hyperkaehler varieties in place of quiver varieties we construct the toric Betti, De Rham and Dolbeault spaces and prove several of the expected properties of the geometry and topology of these varieties. This is joint work with Nick Proudfoot.

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
Arnaud DOUCET 氏 (統計数理研究所)
Interacting Markov chain Monte Carlo Methods for Solving Nonlinear Measure-Valued Equations
[ 講演概要 ]
We present a new class of interacting Markov chain Monte Carlo algorithms for solving numerically discrete-time measure-valued equations. The associated stochastic processes belong to the class of self-interacting Markov chains. In contrast to traditional Markov chains, their time evolution depend on the occupation measure of their past values. This general methodology allows us to provide a natural way to sample from a sequence of target probability measures of increasing complexity. We develop an original theoretical analysis to analyze the behaviour of these iterative algorithms. We establish a variety of convergence results including exponential estimates and a uniform convergence theorem with respect to the number of target distributions. We also illustrate these algorithms in the context of Feynman-Kac distribution flows.
(this is joint work with Professor Pierre Del Moral)
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/02.html

2009年04月21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
Ivan Marin 氏 (Univ. Paris VII)
Some algebraic aspects of KZ systems
[ 講演概要 ]
Knizhnik-Zamolodchikov (KZ) systems enables one
to construct representations of (generalized)
braid groups. While this geometric construction is
now very well understood, it still brings to
attention, or helps constructing, new algebraic objects.
In this talk, we will present some of them, including an
infinitesimal version of Iwahori-Hecke algebras and a
generalization of the Krammer representations of the usual
braid groups.

2009年04月20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) 126号室
鎌田博行 氏 (宮城教育大学)
Indefinite Kähler surfaces of constant scalar curvature

2009年04月18日(土)

東京無限可積分系セミナー

11:00-14:30   数理科学研究科棟(駒場) 117号室
Vladimir Dobrev 氏 (Institute for Nuclear Reserch and Nuclear Energy, Sofia, Bulgaria) 11:00-12:00
Invariant Differential Operators for Non-Compact Lie Groups
[ 講演概要 ]
We present a canonical procedure for the explicit construction of
invariant differential operators. The exposition is for semi-simple
Lie algebras, but is easily generalized to the supersymmetric and
quantum group settings. Especially important is a narrow class of
algebras, which we call 'conformal Lie algebras', which have very
similar properties to the conformal algebras of n-dimensional
Minkowski space-time. Examples are given in detail, including diagrams of
intertwining operators, or equivalently, multiplets of elementary
representations (generalized Verma modules).
笠谷昌弘 氏 (東大数理) 13:30-14:30
TBA
[ 講演概要 ]
TBA

2009年04月16日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 128号室
緒方芳子 氏 (東大数理)
Large Deviations in Quantum Spin Chains

2009年04月15日(水)

講演会

15:30-17:00   数理科学研究科棟(駒場) 470号室
Wilhelm Stannat 氏 (Darmstadt 工科大学)
Invariant measures for stochastic partial differential equations: new a priori estimates and applications

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
Jean JACOD 氏 (Universite Paris VI)
Estimating the successive Blumenthal-Getoor indices for a discretely observed process
[ 講演概要 ]
Letting F be a Levy measure whose "tail" $F ([-x, x])$ admits an expansion $\\sigma_{i\\ge 1} a_i/x^\\beta$ as $x \\rightarrow 0$, we call $\\beta_1 > \\beta_2 >...$ the successive Blumenthal-Getoor indices, since $\\beta_1$ is in this case the usual Blumenthal-Getoor index. This notion may be extended to more general semimartingale. We propose here a method to estimate the $\\beta_i$'s and the coefficients $a_i$'s, or rather their extension for semimartingales, when the underlying semimartingale $X$ is observed at discrete times, on fixed time interval. The asymptotic is when the time-lag goes to $0$. It is then possible to construct consistent estimators for $\\beta_i$ and $a_i$ for those $i$'s such that $\\beta_i > \\beta_1 /2$, whereas it is impossible to do so (even when $X$ is a Levy process) for those $i$'s such that $\\beta_i < \\beta_1 /2$. On the other hand, a central limit theorem for $\\beta_1$ is available only when $\\beta_i < \\beta_1 /2$: consequently, when we can actually consistently estimate some $\\beta_i$'s besides $\\beta_1$ , then no central limit theorem can hold, and correlatively the rates of convergence become quite slow (although one know them explicitly): so the results have some theoretical interest in the sense that they set up bounds on what is actually possible to achieve, but the practical applications are probably quite thin.
(joint with Yacine Ait-Sahalia)
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/00.html

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
Jean JACOD 氏 (Universite Paris VI)
A survey on realized p-variations for semimartingales
[ 講演概要 ]
Let $X$ be a process which is observed at the times $i\\Delta_n$ for $i=0,1,\\ldots,$. If $p>0$ the realized $p$-variation over the time interval $[0, t]$ is

V^n(p)_t=\\sum_{i=1}^{[t/\\Delta_n]}|X_{i\\Delta_n}-X_{(i-1)\\Delta_n}|^p.

The behavior of these $p$-variations when $\\Delta_n ightarrow 0$ (and t is fixed) is now well understood, from the point of view of limits in probability (these are basically old results due to Lepingle) and also for the associated central limit theorem.
The aim of this talk is to review those results, as well as a few extensions (multipower variations, truncated variations). We will put some emphasis on the assumptions on $X$ which are needed, depending on the value of $p$.
[ 参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/00.html

2009年04月14日(火)

講演会

16:30-18:00   数理科学研究科棟(駒場) 056号室
Klaus Niederkruger 氏 (Ecole normale superieure de Lyon)
Resolution of symplectic orbifolds obtained from reduction
[ 講演概要 ]
We present a method to obtain resolutions of symplectic orbifolds arising from symplectic reduction of a Hamiltonian S1-manifold at a regular value. As an application, we show that all isolated cyclic singularities of a symplectic orbifold admit a resolution and that pre-quantizations of symplectic orbifolds are symplectically fillable by a smooth manifold.

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