## 過去の記録

### 2011年01月17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
Dano Kim 氏 (KIAS)
L^2 methods and Skoda division theorems (ENGLISH)
[ 講演概要 ]
Extension of Ohsawa-Takegoshi type and division of Skoda type are two important consequences of the L^2 methods of Hormander, Demailly and others. They are analogous to vanishing theorems of Kodaira type and can be viewed as some refinement of the vanishing. The best illustration of their usefulness up to now is Siu’s proof of invariance of plurigenera without general type assumption. In this talk, we will focus on the division theorem / problem and talk about its currently known cases (old and new). One motivation comes from yet another viewpoint on the finite generation of canonical ring.

#### 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

Asymptotics of the Bergman function for semipositive holomorphic line bundles (JAPANESE)
[ 講演概要 ]
In this talk, an asymptotic expansion of the Bergman function at a degenerate point is given for high powers of semipositive holomorphic line bundles on compact Kahler manifolds, whose Hermitian metric has some kind of quasihomogeneous properties. In the sence of pointwise asymptotics, This expansion is a generalization of the expansion of Tian-Zelditch-Catlin-Lu in the positive line bundle case.

### 2011年01月13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
Robert Coquereaux 氏 (CNRS/CPT)
Global dimensions for fusion categories of type $(G,k)$ (ENGLISH)

### 2011年01月12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
Zhonghua Li 氏 (東京大学大学院数理科学研究科) 16:30-17:30
On regularized double shuffle relation for multiple zeta values (ENGLISH)
[ 講演概要 ]
Multiple zeta values(MZVs) are natural generalizations of Riemann zeta values. There are many rational relations among MZVs. It is conjectured that the regularized double shuffle relations contian all rational relations of MZVs. So other rational relations should be deduced from regularized dhouble shuffle relations. In this talk, we discuss some results on this problem. We define the gamma series accociated to elements satisfying regularized double shuffle relations and give some properties. Moreover we show that the Ohno-Zagier relations can be deduced from regularized double shuffle relations.
Dan Yasaki 氏 (North Carolina University) 17:45-18:45
Spines with View Toward Modular Forms (ENGLISH)
[ 講演概要 ]
The study of an arithmetic group is often aided by the fact that it acts naturally on a nice topological object. One can then use topological or geometric techniques to try to recover arithmetic data. For example, one often studies SL_2(Z) in terms of
its action on the upper half plane. In this talk, we will examine spines, which are the smallest" such spaces for a given arithmetic group. On overview of some known theoretical results and explicit computations will be given.

### 2011年01月11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

The Chas-Sullivan conjecture for a surface of infinite genus (JAPANESE)
[ 講演概要 ]

\\Sigma_{\\infty,1} を境界成分 1 の向きづけられたコンパクト曲面の

の中心が定数ループで張られることを証明する。閉曲面についての

することで証明される。時間が許せば、線型コード図式の空間上の
Lie 代数の構造についても議論したい。

#### 作用素環セミナー

16:30-18:00   数理科学研究科棟(駒場) 122号室
Raphael Ponge 氏 (Univ. Tokyo)
Noncommutative geometry and diffeomorphism-invariant geometries (ENGLISH)

#### 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

http://www.ms.u-tokyo.ac.jp/gcoe/index.html

[ 講演概要 ]

[ 講演参考URL ]
http://www.infsup.jp/utnas/

### 2010年12月22日(水)

#### GCOEセミナー

11:00-12:00   数理科学研究科棟(駒場) 570号室
Mourad Bellassoued 氏 (Faculté des Sciences de Bizerte)
Stability estimates for the anisotropic Schrodinger equations from the Dirichlet to Neumann map (ENGLISH)
[ 講演概要 ]
In this talk we want to obtain stability estimates for the inverse problem of determining the electric potential or the conformal factor in the Schrodinger equations in an anisotropic media with Dirichlet data from measured Neumann boundary observations. This information is enclosed in the dynamical Dirichlet-to-Neumann map associated to the Schrödinger equation. We prove in dimension $n\\geq 2$ that the knowledge of the Dirichlet to Neumann map for the Schrödinger equation measured on the boundary uniquely determines the electric potential and we prove H\\"older-type stability in determining the potential. We prove similar results for the determination of a conformal factor close to 1 (this is a joint work with David Dos Santos Ferreira).

#### 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

[ 講演概要 ]

「ゼータ関数の貼り合わせ」の手法を用いて加藤、Mahesh Kakde 及び

Alfred Weiss も異なる定式化の下で主予想が成立する例を構成している)。

なお、総実代数体の非可換岩澤主予想は、2010年に
Ritter-Weiss 及び Kakde によって一般の場合にも

### 2010年12月21日(火)

#### 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

Some relation between the Weyl module and the crystal basis of the tensor product of fudamental representations (ENGLISH)
[ 講演概要 ]
The Lie algebra defined by the tensor product of a simple Lie algebra and a polynomial ring is called the current algebra, and the Weyl module is defined by a finite dimensional module of the current algebra having some universal property.
The fundamental representation is a irreducible, finite dimensional, level zero integrable representation of the quantized affine algebra, and it is known that this module has a crystal basis.
If the simple Lie algebra is of ADE type, Fourier and Littelamnn has shown that the Weyl module is isomorphic to a module called the Demazure module.
Using this fact, we can easily see that the (\\mathbb{Z}-graded) characters of the Weyl module and the crystal basis of the tensor product of fundamental representations coincides.
In my talk, I will introduce the generalization of this result in the non-simply laced case.
In this case, the result of Fourier and Littelmann does not necessarily true, but we can show the characters of two objects also coincide in this case.
This fact is shown using the Demazure modules and its crystal basis'' called the Demazure crystals.

### 2010年12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) 128号室

ホップ曲面の擬凸状領域について (JAPANESE)
[ 講演概要 ]
2つの複素数a, b (1<|a|\\le|b|)に関するホップ曲面をHとする. Hの実解析的滑らかな境界を持つ擬凸状領域Dのロバン函数 ¥Lambda[z,w] は多重劣調和近似函数であることを示し, 上田の予想について述べる.

#### 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

On the minimal model theory from a viewpoint of numerical invariants (JAPANESE)
[ 講演概要 ]
I will introduce the numerical Kodaira dimension for pseudo-effective divisors after N. Nakayama and explain the minimal model theory of numerical Kodaira dimension zero. I also will talk about the applications. ( partially joint work with B. Lehmann.)

### 2010年12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) 122号室
Marco Merkli 氏 (Memorial Univ. Newfoundland)
Evolution of Quantum Dynamical Systems (ENGLISH)

#### 作用素環セミナー

15:15-16:15   数理科学研究科棟(駒場) 122号室
Nicolas Monod 氏 (EPFL)
Fixed point theorems and derivations (ENGLISH)

#### 講演会

13:00-14:30   数理科学研究科棟(駒場) 123号室
Sebastien Hitier 氏 (BNP Paribas, Head of Quantitative Research, Credit Asia)
Credit Derivatives Modelling and the concept of Background Intensity I (ENGLISH)
[ 講演概要 ]
Session 1: Introducing background intensity models
- Motivation for the concept of background intensity
- The default realisation marker
- Definition of background filtration and background intensity
- Reformulating the H hypothesis, and Kusuoka’s “remark”
- Generalised HJM formula and Credit Risk neutral dynamics

Session 2: Five useful properties of background intensity models
- Generalised HJM formula for credit
- Definition of conditionally independent defaults
- Diversification effects: results on forward loss distribution
- Stronger conditional independence effect for spot loss
- Existence of a canonical copula
- Properties of the portfolio loss copula

#### 講演会

14:40-16:10   数理科学研究科棟(駒場) 123号室
Sebastien Hitier 氏 (BNP Paribas, Head of Quantitative Research, Credit Asia)
Credit Derivatives Modelling and the concept of Background Intensity II (ENGLISH)
[ 講演概要 ]
Session 1: Introducing background intensity models
- Motivation for the concept of background intensity
- The default realisation marker
- Definition of background filtration and background intensity
- Reformulating the H hypothesis, and Kusuoka’s “remark”
- Generalised HJM formula and Credit Risk neutral dynamics

Session 2: Five useful properties of background intensity models
- Generalised HJM formula for credit
- Definition of conditionally independent defaults
- Diversification effects: results on forward loss distribution
- Stronger conditional independence effect for spot loss
- Existence of a canonical copula
- Properties of the portfolio loss copula

### 2010年12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
Kenneth Schackleton 氏 (IPMU)
On the coarse geometry of Teichmueller space (ENGLISH)
[ 講演概要 ]
We discuss the synthetic geometry of the pants graph in
comparison with the Weil-Petersson metric, whose geometry the
pants graph coarsely models following work of Brock’s. We also
restrict our attention to the 5-holed sphere, studying the Gromov
bordification of the pants graph and the dynamics of pseudo-Anosov
mapping classes.

### 2010年12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

[ 講演概要 ]

#### 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
Sergey Fomin 氏 (University of Michigan)
Enumeration of plane curves and labeled floor diagrams (ENGLISH)
[ 講演概要 ]
Floor diagrams are a class of weighted oriented graphs introduced by E. Brugalle and G. Mikhalkin. Tropical geometry arguments yield combinatorial descriptions of (ordinary and relative) Gromov-Witten invariants of projective spaces in terms of floor diagrams and their generalizations. In the case of the projective plane, these descriptions can be used to obtain new formulas for the corresponding enumerative invariants. In particular, we give a proof of Goettsche's polynomiality conjecture for plane curves, and enumerate plane rational curves of given degree passing through given points and having maximal tangency to a given line. On the combinatorial side, we show that labeled floor diagrams of genus 0 are equinumerous to labeled trees, and therefore counted by the celebrated Cayley's formula. The corresponding bijections lead to interpretations of the Kontsevich numbers (the genus-0 Gromov-Witten invariants of the projective plane) in terms of certain statistics on trees.

This is joint work with Grisha Mikhalkin.

### 2010年12月10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) 117号室
-紫綬褒章受章を祝して-

お茶&Coffee&お菓子: 16:00～16:30 (コモンルーム)。

ハミルトン・ヤコビ方程式と結晶成長 (JAPANESE)
[ 講演概要 ]

・ヤコビ方程式を用いるものである。成長に伴いファセットと呼ばれる平らな面が平らな
まま成長できるかどうか安定性の問題は、複雑な形状が生み出されるかといった形態形成
の問題として重要であるが、半導体のような産業技術の問題としても重要である。ハミル
トン・ヤコビ方程式で記述される場合、数学的には時間大域的な解の挙動の問題と考えら
れる。ハミルトニアンが強圧的な場合は力学系的に言えばエルゴード性があることはよく

しないことがわかる。このような数学的成果に触れつつ、結晶成長の問題に対してどのよ
うな貢献ができるかについて述べる。

### 2010年12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) 122号室
Ryszard Nest 氏 (Univ. Copenhagen)
Spectral flow associated to KMS states with periodic KMS group action (ENGLISH)

### 2010年12月07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
Raphael Ponge 氏 (東京大学大学院数理科学研究科)
Diffeomorphism-invariant geometries and noncommutative geometry (ENGLISH)
[ 講演概要 ]
In many geometric situations we may encounter the action of
a group $G$ on a manifold $M$, e.g., in the context of foliations. If
the action is free and proper, then the quotient $M/G$ is a smooth
manifold. However, in general the quotient $M/G$ need not even be
Hausdorff. Furthermore, it is well-known that a manifold has structure
invariant under the full group of diffeomorphisms except the
differentiable structure itself. Under these conditions how can one do
diffeomorphism-invariant geometry?

Noncommutative geometry provides us with the solution of trading the
ill-behaved space $M/G$ for a non-commutative algebra which
essentially plays the role of the algebra of smooth functions on that
space. The local index formula of Atiyah-Singer ultimately holds in
the setting of noncommutative geometry. Using this framework Connes
and Moscovici then obtained in the 90s a striking reformulation of the
local index formula in diffeomorphism-invariant geometry.

An important part the talk will be devoted to reviewing noncommutative
geometry and Connes-Moscovici's index formula. We will then hint to on-
going projects about reformulating the local index formula in two new
geometric settings: biholomorphism-invariant geometry of strictly
pseudo-convex domains and contactomorphism-invariant geometry.

#### 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

http://www.ms.u-tokyo.ac.jp/gcoe/index.html

(JAPANESE)
[ 講演概要 ]

[ 講演参考URL ]
http://www.infsup.jp/utnas/

### 2010年12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

[ 講演概要 ]

### 2010年12月04日(土)

#### 古典解析セミナー

09:30-10:30   数理科学研究科棟(駒場) 056号室