過去の記録

2010年06月10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
Christian Klingenberg 氏 (Wuerzburg 大学 )
Hydrodynamic limit of microscopic particle systems to conservation laws to fluid models
[ 講演概要 ]
In this talk we discuss the hydrodynamic limit of a microscopic description of a fluid to its macroscopic PDE description.

In the first part we consider flow through porous media, i.e. the macroscopic description is a scalar conservation law. Here the new feature is that we allow sudden changes in porosity and thereby the flux may have discontinuities in space. Microscopically this is described through an interacting particle system having only one conserved quantity, namely the total mass. Macroscopically this gives rise to a scalar conservation laws with space dependent flux functions

u_t + f(u, x)_x = 0 .

We are able to derive the PDE together with an entropy condition as a hydrodynamic limit from a microscopic interacting particle system.

In the second part we consider a Hamiltonian system with boundary conditions. Microscopically this is described through a system of coupled oscillators. Macroscopically this will lead to a system of conservation laws, namely the p-system. The proof of the hydrodynamic limit is restricted to smooth solutions. The new feature is that we can derive this with boundary conditions.

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
Mikael Pichot 氏 (IPMU)
Random groups and nonarchimedean lattices (JAPANESE)

2010年06月09日(水)

代数学コロキウム

16:15-17:15   数理科学研究科棟(駒場) 052号室
Richard Hain 氏 (Duke大学)
Universal mixed elliptic motives (ENGLISH)
[ 講演概要 ]
This is joint work with Makoto Matsumoto. A mixed elliptic
motive is a mixed motive (MHS, Galois representation, etc) whose
weight graded quotients are Tate twists of symmetric powers of the the
motive of elliptic curve. A universal mixed elliptic motive is an
object that can be specialized to a mixed elliptic motive for any
elliptic curve and whose specialization to the nodal cubic is a mixed
Tate motive. Universal mixed elliptic motives form a tannakian
category. In this talk I will define universal mixed elliptic motives,
give some fundamental examples, and explain what we know about the
fundamental group of this category. The "geometric part" of this group
is an extension of SL_2 by a prounipotent group that is generated by
Eisenstein series and which has a family of relations for each cusp
form. Although these relations are not known, we have a very good idea
of what they are, thanks to work of Aaron Pollack, who determined
relations between the generators in a very large representation of
this group.

代数学コロキウム

17:30-18:30   数理科学研究科棟(駒場) 056号室
Fabrice Orgogozo 氏 (CNRS, École polytechnique)
エタールコホモロジーの高次順像の一様構成可能性について
(ENGLISH)
[ 講演概要 ]
Z_ℓエタールコホモロジーの捻れとF_ℓコホモロジーの超積の関係を巡り
N. Katz氏の指摘に基づいて、高次順像に於けるℓに対する

(この様な定理は以前よりガバー氏の構想に有った。)
ここでは月並みな方法で有るが、A.J.de Jong氏の定理と

(本講演は「東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とIHESとの双方向同時中継で行います。)

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

[ 講演概要 ]

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

GCOEセミナー

16:30-18:00   数理科学研究科棟(駒場) 002号室

[ 講演概要 ]

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

統計数学セミナー

15:00-16:10   数理科学研究科棟(駒場) 000号室

Weak convergence of Markov chain Monte Carlo method and its application to Yuima (JAPANESE)
[ 講演概要 ]
マルコフチェインモンテカルロ(MCMC)法の収束を MCMC法の弱収束の観点から論じる.とくに,MCMC法に対する マルコチェインのエルゴード性からのアプローチとの比較を行う. これらの収束理論の紹介とともに,幾つかの数値実験を統計ソフトフェアRを用いて考察する. また,MCMC法の弱収束とYuimaパッケージに実装されているadaBayes関数との関連を論じる.

[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/03.html

2010年06月08日(火)

Lie群論・表現論セミナー

17:00-18:30   数理科学研究科棟(駒場) 126号室

Automorphism groups of causal Makarevich spaces (JAPANESE)
[ 講演概要 ]
Let G^ be a simple Lie group of Hermitian type and U^ be a maximal parabolic subgroup of G^ with abelian nilradical. The flag manifold M^= G^/ U^ is the Shilov
boundary of an irreducible bounded symmetric domain of tube type. M^ has the G-invariant causal structure. A causal Makarevich space is, by definition, an open symmetric G-orbit M in M^, endowed with the causal structure induced from that
of the ambient space M^, G being a reductive subgroup of G^. All symmetric cones fall in the class of causal Makarevich spaces.
In this talk, we determine the causal automorphism groups of all causal Makarevich spaces.

2010年06月07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
Xavier Roulleau 氏 (東大数理)
Genus 2 curve configurations on Fano surfaces (ENGLISH)

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06月03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

Fixed Points in the Stone-Cech boundary of Groups (ENGLISH)
[ 講演概要 ]
We discuss the class of discrete groups which admit fixed points under the adjoint action on the Stone-Cech boundary. Such groups have vanishing $L^2$-Betti numbers, and nonamenable ones fail to have property (AO).

GCOEレクチャーズ

16:30-18:00   数理科学研究科棟(駒場) 470号室
Birgit Speh 氏 (Cornel University)
Introduction to the cohomology of locally symmetric spaces 2
(ENGLISH)
[ 講演概要 ]
I will give an introduction to the cohomology of noncompact locally symmetric spaces $X_\\Gamma =K \\backslash G / \\Gamma$.
If $X_\\Gamma$ is cocompact this cohomology can be expressed as the $(\\bg,K)$-cohomology of automorphic representations. I will explain how representation theory and automorphic forms can be used to study the cohomology in this case.

[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html

2010年06月02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

On some algebraic properties of CM-types of CM-fields and their
reflex fields (JAPANESE)
[ 講演概要 ]
Shimura and Taniyama proved in their theory of complex
multiplication that the moduli of abelian varieties of a CM-type and their
torsion points generate an abelian extension, not of the field of complex
multiplication, but of a reflex field of the field. In this talk, I
introduce some algebraic properties of CM-types, half norm maps that might
shed new light on reflex fields.

For a CM-field $K$ and its Galois closure $K^c$ over the rational field $Q$,
there is a canonical embedding of $Gal (K^c/Q)$ into $(Z/2Z)^n \\rtimes S_n$.
Using properties of the embedding, a set of CM-types $\\Phi$ of $K$ and their
dual CM-types $(K, \\Phi)$ is equipped with a combinatorial structure. This
makes it much easier to handle a whole set of CM-types than an individual
CM-type.

I present a theorem that shows the combinatorial structure of the dual
CM-types is isomorphic to that of a Pfister form.

2010年06月01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: 16:30 - 17:00 コモンルーム

On Fatou-Julia decompositions (JAPANESE)
[ 講演概要 ]
We will explain that Fatou-Julia decompositions can be
introduced in a unified manner to several kinds of one-dimensional
complex dynamical systems, which include the action of Kleinian groups,
iteration of holomorphic mappings and complex codimension-one foliations.
In this talk we will restrict ourselves mostly to the cases where the
dynamical systems have a certain compactness, however, we will mention
how to deal with dynamical systems without compactness.

GCOEレクチャーズ

16:30-18:00   数理科学研究科棟(駒場) 126号室
Birgit Speh 氏 (Cornel University)
Introduction to the cohomology of locally symmetric spaces
(ENGLISH)
[ 講演概要 ]
I will give an introduction to the cohomology of noncompact locally symmetric spaces $X_\\Gamma =K \\backslash G / \\Gamma$.
If $X_\\Gamma$ is cocompact this cohomology can be expressed as the $(g,K)$-cohomology of automorphic representations. I will explain how representation theory and automorphic forms can be used to study the cohomology in this case.
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html

2010年05月31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

On Pfaffian Calabi-Yau Varieties and Mirror Symmetry (JAPANESE)
[ 講演概要 ]
We construct new smooth CY 3-folds with 1-dimensional Kaehler moduli and
determine their fundamental topological invariants. The existence of CY
3-folds with the computed invariants was previously conjectured. We then
report mirror symmetry for these non-complete intersection CY 3-folds.
We explicitly build their mirror partners, some of which have 2 LCSLs,
and carry out instanton computations for g=0,1.

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

Singularities and analytic torsion (JAPANESE)

2010年05月28日(金)

古典解析セミナー

16:30-18:00   数理科学研究科棟(駒場) 126号室

[ 講演概要 ]
はじめにこれまでに調べてきた3次元アフィン空間の17種類の単純型斎藤自由因子に沿って対数的極をもつ一意化方程式について概観する。つぎにこれらの斎藤自由因子の補空間の基本群と一意化方程式の関係を論じる。Type Biii)の場合に基本群が可換になる。この場合に一意化方程式の解を初等関数をつかって表示することを試みる。

2010年05月27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
Catherine Oikonomides 氏 (東大数理)
The C*-algebra of codimension one foliations which are almost without holonomy (ENGLISH)

2010年05月26日(水)

統計数学セミナー

16:20-17:30   数理科学研究科棟(駒場) 000号室

R-Yuimaパッケージによるファイナンス高頻度データ解析とシミュレーション (JAPANESE)
[ 講演概要 ]
ファイナンス高頻度データなど、必ずしも等間隔でサンプルされていない時系列データを効率的に処理するツールとして、R言語のzoo,
xtsそしてyuimaパッケージをチュートリアル的に紹介する。ヘッジ戦略のバックテストなどを例示する。またyuimaに実装されている新しい確率微分方程式モデルのシミュレーション法を理論的な利点とともに解説する。
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/02.html

PDE実解析研究会

10:30-11:30   数理科学研究科棟(駒場) 056号室

Giovanni Pisante 氏 (Department of Mathematics
Hokkaido University)
A SELECTION CRITERION FOR SOLUTIONS OF A
SYSTEM OF EIKONAL EQUATIONS
(ENGLISH)
[ 講演概要 ]
We deal with the system of eikonal equations |ðu/ðx1|=1, |ðu/ðx2|=1 in a planar Lipschitz domain with zero boundary condition. Exploiting the classical pyramidal construction introduced by Cellina, it is easy to prove that there exist infinitely many Lipschitz solutions. Then, the natural problem that has arisen in this framework is to find a way to select and characterize a particular meaningful class of solutions.
We propose a variational method to select the class of solutions which minimize the discontinuity set of the gradient. More precisely we select an optimal weighted measure for the jump set of the second derivatives of a given solution v of the system and we prove the existence of minimizers of the corresponding variational problem.

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

Existence and non-existence of global solutions for a discrete semilinear heat equation (JAPANESE)
[ 講演概要 ]

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

GCOEセミナー

16:30-18:00   数理科学研究科棟(駒場) 002号室

Existence and non-existence of global solutions for a discrete semilinear heat equation (JAPANESE)
[ 講演概要 ]

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

2010年05月25日(火)

Lie群論・表現論セミナー

17:00-18:00   数理科学研究科棟(駒場) 126号室
5月24日(月)-28日(金)に平賀氏の集中講義が行われます

(京都大学)
On endoscopy, packets, and invariants (JAPANESE)
[ 講演概要 ]
The theory of endoscopy came out of the Langlands functoriality and the trace formula.
In this talk, I will briefly explain what the endoscopy is, and talk about packet, formal degree and Whittaker normalization of transfer.
I would like to talk about the connection between these topics and the endoscopy.

2010年05月24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

A counterexample of the birational Torelli problem via Fourier--Mukai transforms (JAPANESE)
[ 講演概要 ]
We study the Fourier--Mukai numbers of rational elliptic surfaces. As
its application, we give an example of a pair of minimal 3-folds $X$
with Kodaira dimensions 1, $h^1(O_X)=h^2(O_X)=0$ such that they are
mutually derived equivalent, deformation equivalent, but not
birationally equivalent. It also supplies a counterexample of the
birational Torelli problem.