過去の記録

過去の記録 ~11/11本日 11/12 | 今後の予定 11/13~

2010年11月26日(金)

Kavli IPMU Komaba Seminar

14:40-16:10   数理科学研究科棟(駒場) 002号室
松村 朝雄 氏 (Cornell University)
Hamiltonian torus actions on orbifolds and orbifold-GKM theorem (joint
work with T. Holm) (JAPANESE)
[ 講演概要 ]
When a symplectic manifold M carries a Hamiltonian torus R action, the
injectivity theorem states that the R-equivariant cohomology of M is a
subring of the one of the fixed points and the GKM theorem allows us
to compute this subring by only using the data of 1-dimensional
orbits. The results in the first part of this talk are a
generalization of this technique to Hamiltonian R actions on orbifolds
and an application to the computation of the equivariant cohomology of
toric orbifolds. In the second part, we will introduce the equivariant
Chen-Ruan cohomology ring which is a symplectic invariant of the
action on the orbifold and explain the injectivity/GKM theorem for this ring.

2010年11月25日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
戸松玲治 氏 (東京理科大)
Kac 環の作用の分類 (JAPANESE)

2010年11月18日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
Jean Roydor 氏 (Univ. Tokyo)
Perturbation of dual operator algebras and similarity (ENGLISH)

2010年11月17日(水)

代数学コロキウム

16:30-17:30   数理科学研究科棟(駒場) 056号室
原瀬 晋 氏 (東京大学大学院数理科学研究科)
F_2-線形擬似乱数発生法の評価に用いる格子の簡約基底計算の高速化 (JAPANESE)
[ 講演概要 ]
(部分的に松本眞氏、斎藤睦夫氏との共同研究)
擬似乱数発生法とは、あたかも乱数であるかのようにふるまう数列を、計算機上で
決定的なアルゴリズムにより発生する方法のことである。擬似乱数を評価する規準
の一つとして、高次元均等分布性がしばしば用いられる。メルセンヌツイスター法
を含む二元体上の線形擬似乱数発生法に対しては、上位ビットの均等分布の次元を
具体的に計算することが可能であり、擬似乱数の出力列から構成したある格子の簡
約基底を求める問題(二元体係数形式的冪級数体の数の幾何)に帰着される(Couture-
L'Ecuyer-Tezuka(1993)およびTezuka(1994))。本研究では、前述の格子を用いた
計算法を発展させ、
(i) 冪級数成分の格子点を擬似乱数発生器の状態ベクトルで表現する、
(ii) 射影を用いてv次元簡約基底からv-1次元簡約基底を計算する、
(iii) 効率的な格子簡約アルゴリズムを適用する、
などの手法を導入し、均等分布の次元計算の高速化を提案する。この方法は、
Couture-L'Ecuyer(2000)による双対格子を用いた改良よりも計算量が少なく、計算機
実験でも10倍程度の高速化が得られたことを紹介する。この結果は、ワードサイズの
大きな擬似乱数発生法の設計や擬似乱数の並列発生スキームなどへの応用が考えられる。

2010年11月16日(火)

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
本セミナーは、グローバルCOE事業「数学新展開の研究教育拠点」(東京大学)の援助を受け、GCOEセミナーして行われています。
https://www.ms.u-tokyo.ac.jp/gcoe/index.html

劉雪峰 氏 (早稲田大学/CREST, JST)
任意多角形領域上での楕円型作用素に対する精度保証付き評価 (JAPANESE)
[ 講演参考URL ]
http://www.infsup.jp/utnas/

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
伊藤 昇 氏 (早稲田大学)
On a colored Khovanov bicomplex (JAPANESE)
[ 講演概要 ]
Jones 多項式の Khovanov ホモロジーと関連理論が近年活発に
研究されている.Jons 多項式の一般化である colored Jones多項式についても
Khovanov により対応するコホモロジーが導入され,特に Mackaay と Turner
や Beliakova とWehrli の研究を通し発展した.しかし,このコホモロジーが持つ
2つの境界作用素によって,Khovanov型の複体で2重複体となるものが構成
できるのかは問題として残されていた.もしあるならば Khovanov 型のホモロジーが
Total complexのコホモロジーに収束するスペクトル系列の第2項として理解される.
この問題意識は Beliakova と Wehliの論文によって紹介された.今回はそれに
対して一つの答えを与える.また似た文脈で colored Jones 多項式の別のスペクトル
系列からは絡み目のcolored Rasmussen 不変量が自然に出てくることも時間が許せば
紹介したい.

代数幾何学セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
いつもと曜日・時間・場所が異なります
Viacheslav Nikulin 氏 (Univ Liverpool and Steklov Moscow)
Self-corresponences of K3 surfaces via moduli of sheaves (ENGLISH)
[ 講演概要 ]
In series of our papers with Carlo Madonna (2002--2008) we described self-correspondences via moduli of sheaves with primitive isotropic Mukai vectors for K3 surfaces with Picard number one or two. Here, we give a natural and functorial answer to the same problem for arbitrary Picard number of K3 surfaces. As an application, we characterize in terms of self-correspondences via moduli of sheaves K3 surfaces with reflective Picard lattices, that is when the automorphism group of the lattice is generated by reflections up to finite index. See some details in arXiv:0810.2945.

代数幾何学セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
Viacheslav Nikulin 氏 (Univ Liverpool and Steklov Moscow)
Self-corresponences of K3 surfaces via moduli of sheaves (ENGLISH)
[ 講演概要 ]
In series of our papers with Carlo Madonna (2002--2008) we described self-correspondences via moduli of sheaves with primitive isotropic Mukai vectors for K3 surfaces with Picard number one or two. Here, we give a natural and functorial answer to the same problem for arbitrary Picard number of K3 surfaces. As an application, we characterize in terms of self-correspondences via moduli of sheaves K3 surfaces with reflective Picard lattices, that is when the automorphism group of the lattice is generated by reflections up to finite index. See some details in arXiv:0810.2945.

解析学火曜セミナー

16:00-18:30   数理科学研究科棟(駒場) 123号室
GCOE miniworkshopと合同
打越敬祐 氏 (防衛大学) 16:00-16:45
Hyperfunctions and vortex sheets (ENGLISH)
L. Boutet de Monvel 氏 (University of Paris 6) 17:00-18:30
Residual trace and equivariant asymptotic trace of Toeplitz operators (ENGLISH)

2010年11月15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
諏訪 立雄 氏 (北大理*)
Excess intersections and residues in improper dimension (JAPANESE)
[ 講演概要 ]
This talk concerns localization of characteristic classes and associated residues, in the context of intersection theory and residue theory of singular holomorphic foliations. The localization comes from the vanishing of certain characteristic forms, usually caused by the existence of some geometric object, away from the "singular set" of the object. This gives rise to residues in the homology of the singular set and residue theorems relating local and global invariants. In the generic situation, i.e., if the dimension of the singular set is "proper", we have a reasonable understanding of the residues. We indicate how to cope with the problem when the dimension is "excessive" (partly a joint work with F. Bracci).

代数幾何学セミナー

16:40-18:10   数理科学研究科棟(駒場) 126号室
吉冨 修平 氏 (東大数理)
Generators of tropical modules (JAPANESE)
[ 講演概要 ]
We study polytopes in a tropical projective space $X$. By Joswig and Kulas, a real convex polytope in $X$ is a tropical simplex, and therefore it is the tropically convex hull of at most $n+1$ points. We show a generalization of this result. It is given using tropical modules and its dual modules. The main interest is
the number of generators of a tropical module.

2010年11月09日(火)

トポロジー火曜セミナー

17:00-18:00   数理科学研究科棟(駒場) 056号室
Tea: 16:40 - 17:00 コモンルーム
大鹿 健一 氏 (大阪大学)
Characterising bumping points on deformation spaces of Kleinian groups (JAPANESE)
[ 講演概要 ]
Klein群の変形空間はその内部の相異なる成分がbump,あるいは同一成分が bumpすることがあることが知られている.
Anderson-Canary-McCulloughの研究により,いかなる成分がbumpするかはわかっている.
本講演ではどのような点でbumpするのかの条件を与える.

2010年11月08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
辻 元 氏 (上智大学)
Variation of canonical measures under Kaehler deformations (JAPANESE)

GCOEレクチャーズ

16:30-18:00   数理科学研究科棟(駒場) 128号室
Michael Eastwood 氏 (Australian National University)
Invariant differential operators on the sphere (ENGLISH)
[ 講演概要 ]
The circle is acted upon by the rotation group SO(2) and there are plenty of differential operators invariant under this action. But the circle is also acted upon by SL(2,R) and this larger symmetry group cuts down the list of invariant differential operators to something smaller but more interesting! I shall explain what happens and how this phenomenon generalises to spheres. These constructions are part of a general theory but have numerous unexpected applications, for example in suggesting a new stable finite-element scheme in linearised elasticity (due to Arnold, Falk, and Winther).
[ 講演参考URL ]
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar2010.html#20101102eastwood

2010年11月05日(金)

GCOEレクチャーズ

16:30-18:00   数理科学研究科棟(駒場) 123号室
Michael Eastwood 氏 (Australian National University)
How to recognise the geodesics of a metric connection (ENGLISH)
[ 講演概要 ]
The geodesics on a Riemannian manifold form a distinguished family of curves, one in every direction through every point. Sometimes two metrics can provide the same family of curves: the Euclidean metric and the round metric on the hemisphere have this property. It is also possible that a family of curves does not arise from a metric at all. Following a classical procedure due to Roger Liouville, I shall explain how to tell these cases apart on a surface. This is joint work with Robert Bryant and Maciej Dunajski.
[ 講演参考URL ]
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar2010.html#20101102eastwood

2010年11月04日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
緒方芳子 氏 (東大数理)
Nonequilibrium Statistical Mechanics (JAPANESE)

講演会

10:40-12:10   数理科学研究科棟(駒場) 123号室
Jean Meyer 氏, 久松康子 氏 (BNPパリバ証券キャピタルマーケッツ・リスク管理部)
Market, Liquidity and Counterparty Risk (ENGLISH)
[ 講演概要 ]
1. Introduction to the market risk

- Introduction to the Risk Management
in the Financial institutions
- Overview of the main market risks

2. Market & Liquidity Risks –Basics

-Presentation of the main Greeks
-Focus on volatility risk
-Focus on correlation risk
-Conclusion (common features of the market risks)

3. Risk measure

- Stress test
- Value at risk
- Risks measure for counterparty risk

2010年11月02日(火)

講演会

13:00-16:10   数理科学研究科棟(駒場) 122号室
Vladimir Bogachev 氏 (Moscow)
The Malliavin calculus on configuration spaces and applications (ENGLISH)
[ 講演概要 ]
It is planned to discuss first a general scheme of the Malliavin
calculus on an abstract measurable
manifold with minimal assumptions about the manifold.
Then a practical realization of this scheme will be discussed in
several concrete examples with emphasis
on configuration spaces, i.e., spaces of locally finite configurations
in a given manifold (for example, just
a finite-dimensional Euclidean space), which can be alternatively
described as the spaces of integer-valued
discrete measures equipped with suitable differential structures.
No acquaintance with the Malliavin calculus and differential geometry
is assumed.

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
Daniel Ruberman 氏 (Brandeis University)
Periodic-end manifolds and SW theory (ENGLISH)
[ 講演概要 ]
We study an extension of Seiberg-Witten invariants to
4-manifolds with the homology of S^1 \\times S^3. This extension has
many potential applications in low-dimensional topology, including the
study of the homology cobordism group. Because b_2^+ =0, the usual
strategy for defining invariants does not work--one cannot disregard
reducible solutions. In fact, the count of solutions can jump in a
family of metrics or perturbations. To remedy this, we define an
index-theoretic counter-term that jumps by the same amount. The
counterterm is the index of the Dirac operator on a manifold with a
periodic end modeled at infinity by the infinite cyclic cover of the
manifold. This is joint work with Tomasz Mrowka and Nikolai Saveliev.

Lie群論・表現論セミナー

16:30-18:00   数理科学研究科棟(駒場) 126号室
Michael Eastwood 氏 (University of Adelaide)
Twistor theory and the harmonic hull (ENGLISH)
[ 講演概要 ]
Harmonic functions are real-analytic and so automatically extend from being functions of real variables to being functions of complex variables. But how far do they extend? This question may be answered by twistor theory, the Penrose transform, and associated geometry. I shall base the constructions on a formula of Bateman from 1904. This is joint work with Feng Xu.

2010年11月01日(月)

代数幾何学セミナー

16:40-18:10   数理科学研究科棟(駒場) 126号室
伊藤 敦 氏 (東大数理)
How to estimate Seshadri constants (JAPANESE)
[ 講演概要 ]
Seshadri constant is an invariant which measures the positivities of ample line bundles. This relates with adjoint bundles, Nagata conjecture, slope stabilities, Gromov width (an invariant of symplectic manifolds) and so on. But it is very diffiult to compute or estimate Seshadri constants in general, especially in higher dimension.
In this talk, we first study Seshadri constants of toric varieties, and next consider about non-toric cases using toric degenerations. For example, good estimations are obtained for complete intersections in projective spaces.

講演会

16:00-18:15   数理科学研究科棟(駒場) 270号室
Michel Cristofol 氏 (マルセイユ大学) 16:00-17:00
Inverse problems in non linear parabolic equations : Two differents approaches (ENGLISH)
[ 講演参考URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/abstractTokyo.pdf
Patricia Gaitan 氏 (マルセイユ大学) 17:15-18:15
Inverse Problems for parabolic System
(ENGLISH)
[ 講演概要 ]
I will present a review of stability and controllability results for linear parabolic coupled systems with coupling of first and zeroth-order terms by data of reduced number of components. The key ingredients are global Carleman estimates.

2010年10月29日(金)

談話会・数理科学講演会

16:30-17:30   数理科学研究科棟(駒場) 002号室
*** 通常とは部屋が異なります。ご注意ください ***
お茶&Coffee&お菓子: 16:00~16:30 (コモンルーム)。

Robin Graham 氏 (University of Washington)
Ambient metrics and exceptional holonomy (ENGLISH)
[ 講演概要 ]
The holonomy of a pseudo-Riemannian metric is a subgroup of the orthogonal group which measures the structure preserved by parallel translation. Construction of pseudo-Riemannian metrics whose holonomy is an exceptional Lie group has been of great interest in recent years. This talk will outline a construction of metrics in dimension 7 whose holonomy is contained in the split real form of the exceptional group $G_2$. The datum for the construction is a generic real-analytic 2-plane field on a manifold of dimension 5; the metric in dimension 7 arises as the ambient metric of a conformal structure on the 5-manifold defined by Nurowski in terms of the 2-plane field.

2010年10月28日(木)

作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
山下真 氏 (東大数理)
Type III representations of the infinite symmetric group (ENGLISH)
[ 講演概要 ]
Based on earlier results about the structure of the II$_1$ representations of the infinite symmetric group, we investigate its type III representations and the related inclusion of von Neumann algebras of type III.

講演会

10:40-12:10   数理科学研究科棟(駒場) 123号室
Jean Meyer 氏, 久松康子 氏 (BNPパリバ証券キャピタルマーケッツ・リスク管理部)
Market, Liquidity and Counterparty Risk (ENGLISH)
[ 講演概要 ]
1. Introduction to the market risk

- Introduction to the Risk Management
in the Financial institutions
- Overview of the main market risks

2. Market & Liquidity Risks –Basics

-Presentation of the main Greeks
-Focus on volatility risk
-Focus on correlation risk
-Conclusion (common features of the market risks)

3. Risk measure

- Stress test
- Value at risk
- Risks measure for counterparty risk

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