過去の記録

過去の記録 ~05/21本日 05/22 | 今後の予定 05/23~

代数幾何学セミナー

15:00-16:00   数理科学研究科棟(駒場) 122号室
Dmitry Kaledin 氏 (Steklov Institute)
p-adic Hodge theory in the non-commutative setting
[ 講演概要 ]
We will explain what is the natural replacement of the notion of Hodge structure in the p-adic setting, and how to construct such a structure for non-commutative manifolds (something which at present cannot be done for the usual Hodge structures, but works perfectly well for the p-adic analog).

2007年10月09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
浅岡 正幸 氏 (京都大学大学院理学研究科)
Classification of codimension-one locally free actions of the affine group of the real line.
[ 講演概要 ]
By GA, we denote the group of affine and orientation-preserving transformations
of the real line. In this talk, I will report on classification of locally free action of
GA on closed three manifolds, which I obtained recently. In 1979, E.Ghys proved
that if such an action preserves a volume, then it is smoothly conjugate to a homogeneous action. However, it was unknown whether non-homogeneous action exists. As a consequence of the classification, we will see that the unit tangent bundle of a closed surface of higher genus admits a finite-parameter family of
non-homogeneous actions.

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 Pevzner 氏 (Reims University and University of Tokyo)
Rankin-Cohen brackets and covariant quantization
[ 講演概要 ]
The particular geometric structure of causal symmetric spaces permits the definition of a covariant quantization of these homogeneous manifolds.
Composition formulae (#-products) of quantizad operators give rise to a new interpretation of Rankin-Cohen brackets and allow to connect them with the branching laws of tensor products of holomorphic discrete series representations.
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html

2007年10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) 056号室
Gandalf Lechner 氏 (Erwin Schroedinger Institute)
Local nets of von Neumann algebras and modular theory

2007年10月02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
Pablo Ramacher 氏 (Gottingen University)


Invariant integral operators on affine G-varieties and their kernels
[ 講演概要 ]
We consider certain invariant integral operators on a smooth affine variety M carrying the action of a reductive algebraic group G, and assume that G acts on M with an open orbit. Then M is isomorphic to a homogeneous vector bundle, and can locally be described via the theory of prehomogenous vector spaces. We then study the Schwartz kernels of the considered operators, and give a description of their singularities using the calculus of b-pseudodifferential operators developed by Melrose. In particular, the restrictions of the kernels to the diagonal can be described in terms of local zeta functions.
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html

2007年09月28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) 123号室
お茶&Coffee&お菓子: 16:00~16:30(コモンルーム)
Marko Tadic' 氏 (University of Zagreb)
Irreducible unitary representations and automorphic forms

[ 講演概要 ]
Unitary representations of adelic groups in the spaces of automorphic forms are big source of important irreducible unitary representations of classical groups over local fields.

We shall present classifications of some classes of irreducible unitary representations (older, as well as quite new), describe
isolated unitary representations among them, and discuss which of them can be obtained from spaces of automorphic forms.

2007年09月26日(水)

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
Grigory Mikhalkin 氏 (Toronto大学)
Floor diagrams and enumeration of tropical curves
[ 講演概要 ]
The enumerative problems considered in this talk are finding the number of curves in projective spaces (over complex, real and tropical numbers) of given genus and degree constrained by certain incidence conditions (e.g. passing via points or lines). Floor diagrams are a combinatorial tool that reduces an enumerative problem in dimension n to the corresponding problem n dimension n-1. Floor diagrams give a constructive (and rather efficient) way to find all tropical curves for a given enumerative problem. And once we have a tropical solution of the problem we can use it to solve the corresponding problems over the complex and real numbers.

2007年09月19日(水)

代数学コロキウム

16:30-17:30   数理科学研究科棟(駒場) 117号室
Gereon Quick 氏 (Universitaet Muenster)
Etale cobordism
[ 講演概要 ]
We define and study a new candidate of etale topological cohomology theories for schemes over a field of abritrary characteristic: etale cobordism. As etale K-theory is related to algebraic K-theory, etale cobordism is related to algebraic cobordism of Voevodsky and Levine/Morel. It shares some nice properties of topological theories, e.g. it is equipped with an Atiyah-Hirzebruch spectral sequence from etale cohomology. We discuss in particular a comparison theorem between etale and algebraic cobordism after inverting a Bott element and, finally, we give an outlook to further possible applications of this theory.

2007年09月15日(土)

保型形式の整数論月例セミナー

13:30-16:00   数理科学研究科棟(駒場) 117号室
長谷川泰子 氏 (東京大学数理科学) 13:30-14:30
Siegl principal series Whittaker functions on $Sp(2,\\mathbf{R})$
(部屋は056室)
[ 講演概要 ]
2次シンプレクティック群のSiegel極大放物型部分群から誘導された一般型主系列表現に対するWhittaker関数の級数表示と積分表示を与えることを目的とし,Whittaker関数の満たす微分評定式を与え,その解の構成に向けて現在進めている研究の方針を述べる.
(部屋は,冷房効く056室に変更です)
市川尚志 氏 (佐賀大学理工学部) 15:00-16:00
A higher rank version of Abel-Jacobi's theorem (Room 056)
[ 講演概要 ]
極大退化曲線に近いリーマン面上のベクトル束とそのモジュライについて話す.次数0の安定ベクトル束が,リーマン面を一意化するショットキー群の線形表現から得られることを述べ,ショットキー群の線形表現の空間とベクトル束のモジュライ空間の関係を,アーベル・ヤコビの定理,フェアリンデ公式を用いて考察する.
(部屋は117号室です)

2007年09月12日(水)

代数幾何学セミナー

15:00-18:00   数理科学研究科棟(駒場) 117号室
代数学コロキウムとの合同講演会です.
E. Lau 氏 (Univ. of Bielefeld) 15:00-15:45
Classification of p-divisible groups by displays and duality
T. Zink 氏 (Univ. of Bielefeld) 16:00-16:45
Applications of the theory of displays
E. Looijenga 氏 (Univ. of Utrecht) 17:00-18:00
Presentation of mapping class groups from algebraic geometry
[ 講演概要 ]
A presentation of the mapping class group of a genus g surface with one hole is due to Wajnryb with later improvements due to M. Matsumoto. The generators are Dehn twists defined by 2g+1 closed curves on the surface. The relations involving only two Dehn twists are the familiar Artin relations, we show that those involving more than two can be derived from algebro-geometry considerations.

代数学コロキウム

15:00-18:00   数理科学研究科棟(駒場) 117号室
代数幾何学セミナーとの合同講演会です
E. Lau 氏 (Univ. of Bielefeld) 15:00-15:45
Classification of p-divisible groups by displays and duality
T. Zink 氏 (Univ. of Bielefeld) 16:00-16:45
Applications of the theory of displays
E. Looijenga 氏 (Univ. of Utrecht) 17:00-18:00
Presentation of mapping class groups from algebraic geometry
[ 講演概要 ]
A presentation of the mapping class group of a genus g surface with one hole is due to Wajnryb with later improvements due to M. Matsumoto. The generators are Dehn twists defined by 2g+1 closed curves on the surface. The relations involving only two Dehn twists are the familiar Artin relations, we show that those involving more than two can be derived from algebro-geometry considerations.

2007年09月05日(水)

PDE実解析研究会

10:30-11:30   数理科学研究科棟(駒場) 056号室
Reinhard Farwig 氏 (Darmstadt University of Technology)
Reguarity of Weak Solutions to the Navier-Stokes System beyond Serrin's Criterion
[ 講演概要 ]
Consider a weak instationary solution $u(x,t)$ of the Navier-Stokes equations in a domain $\\Omega \\subset \\mathbb{R}^3$ in the sense of Leray-Hopf. As is well-known, $u$ is is unique and regular if $u\\in L^s(0,T;L^q(\\Omega))$ satisfies the {\\it strong energy inequality} and $s,q$ satisfy Serrin's condition $\\frac{2}{s} + \\frac{3}{q}=1$, $s>2,\\, q>3$. Now consider $u$ such that $$u\\in L^r(0,T;L^q(\\Omega))\\quad \\mbox{ where }\\quad \\frac{2}{r} + \\frac{3}{q}>1$$ and has a sufficiently small norm in $L^r(0,T;L^q(\\Omega))$. Then we will prove that $u$ is regular. Similar results of local rather than global type in space will be proved provided that $u$ satisfies the {\\it localized energy inequality}. Finally H\\"older continuity of the kinetic energy in time will imply regularity.

The proofs use local in time regularity results which are based on the {\\it theory of very weak solutions} and on uniqueness arguments for weak solutions.
[ 講演参考URL ]
http://coe.math.sci.hokudai.ac.jp/sympo/pde_ra/index.html

2007年08月29日(水)

代数幾何学セミナー

17:00-18:00   数理科学研究科棟(駒場) 128号室
Valery Alexeev 氏 (Georgia大学)
Computations on the moduli spaces of weighted log pairs

2007年08月27日(月)

代数学コロキウム

16:30-17:30   数理科学研究科棟(駒場) 002号室
Steven Zucker 氏 (Johns Hopkins大学)
The reductive Borel-Serre motive

2007年08月02日(木)

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
De-Qi Zhang 氏 (Singapore大学)
Dynamics of automorphisms on algebraic varieties
[ 講演概要 ]
The building blocks of automorphisms / endomorphisms of compact varieties are determined --- an algebro geometric approach towards dynamics.

2007年07月25日(水)

統計数学セミナー

16:20-17:30   数理科学研究科棟(駒場) 122号室
小林 景 氏 (統計数理研究所, 学振特別研究員)
大規模ランダム行列のスペクトル理論とデータ解析への応用(Review)
[ 講演概要 ]
The empirical spectral distribution of random matrices have been studied since Wigner's pioneering work on the semicircular law in the 1950's. The result says that the empirical spectral distribution of a symmetric matrix with i.i.d. random elements converges to the semicircular law as the size of the matrix becomes large. Though this result is beautiful in theory, its application has been limited to a few problems in nuclear physics and coding theory. The next breakthrough was the Marcenko-Pastur (M-P) law for the asymptotic spectral distribution of sample covariance matrices. The M-P law has found more applications, in particular high dimensional statistical data analysis, than the semicircular law.

In this talk I will first review these two significant results. Each of them has three completely different proofs. Then I will explain several other theoretical results that have mostly been studied this decade. Finally, I will present some of the applications of these results. This review is partly based on lectures on random matrices given by P. Bickel, N. El-Karoui and A. Guionnet, and also some seminars at UC Berkeley.

(# This talk is almost the same as the talk I gave at ISM on June 1.)
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2007/05.html

2007年07月20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) 123号室
お茶&Coffee&お菓子: 16:00~16:30(コモンルーム)
和達三樹 氏 (東京理科大学理学部物理学科)
ソリトン物理はおもしろい---スピノル型ボーズ・アインシュタイン凝縮体におけるソリトン

2007年07月19日(木)

アジア数学史セミナー

17:00-18:30   数理科学研究科棟(駒場) 123号室
李 佳女華 氏 (東京大学大学院総合文化研究科)
幕末・明治初期の日本における西洋数学の導入と漢訳西洋数学書籍
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kawazumi/asia.html

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
小沢登高 氏 (東大数理)
On a class of II$_1$ factors with at most one Cartan subalgebra

2007年07月18日(水)

代数学コロキウム

16:30-17:30   数理科学研究科棟(駒場) 117号室
梶原 健 氏 (横浜国立大学)
Tropical toric varieties

統計数学セミナー

16:20-17:30   数理科学研究科棟(駒場) 122号室
増田 弘毅 氏 (九州大学大学院数理学研究院)
Easy full-joint estimators of stable processes
[ 講演概要 ]
安定レヴィ過程からの高頻度観測に基づいた同時推定に関しては,尤度比確率場の漸近挙動は安易に二次項の観測情報量まで見ただけでは解明されず,最尤推定量の典型的な“良い漸近挙動”が保証されないことが分かっている.本発表では,標本メディアンおよび標本メディアンのプラグイン型統計量の漸近挙動に基づき,モデルに入る全パラメータの同時推定を可能とする計算容易な推定量の構成法を紹介し,正則な漸近共分散行列を有する漸近正規性を導出する.推定量の有限標本での挙動を数値実験で検証する.時間があれば,非対称安定レヴィ過程の場合に関して分かっている事柄についても触れる.
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2007/04.html

2007年07月17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
松村 朝雄 氏 (東京大学大学院数理科学研究科)
Orbifold Cohomology of Wreath Product Orbifolds and
Cohomological HyperKahler Resolution Conjecture
[ 講演概要 ]
Chen-Ruan orbifold cohomology ring was introduced in 2000 as
the degree zero genus zero orbifold Gromov-Witten invariants with
three marked points. We will review its construction in the case of
global quotient orbifolds, following Fantechi-Gottsche and
Jarvis-Kaufmann-Kimura. We will describe the orbifold cohomology of
wreath product orbifolds and explain its application to Ruan's
cohomological hyperKahler resolution conjecture.

2007年07月12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
酒匂宏樹 氏 (東大数理)
Normalizers of MASAs and irreducible subfactors

2007年07月11日(水)

代数学コロキウム

16:30-17:30   数理科学研究科棟(駒場) 117号室
Andreas Rosenschon 氏 (University of Alberta)
Algebraic cycles on products of elliptic curves over p-adic fields

2007年07月10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
Danny C. Calegari 氏 (California Institute of Technology)
Combable functions, quasimorphisms, and the central limit theorem
(joint with Koji Fujiwara)

[ 講演概要 ]
Quasimorphisms on groups are dual to stable commutator length,
and detect extremal phenomena in topology and dynamics. In typical groups
(even in a free group) stable commutator length is very difficult to
calculate, because the space of quasimorphisms is too large to study
directly without adding more structure.
In this talk, we show that a large class of quasimorphisms - the so-called
"counting quasimorphisms" on word-hyperbolic groups - can be effectively
described using simple machines called finite state automata. From this,
and from the ergodic theory of finite directed graphs, one can deduce a
number of properties about the statistical distribution of the values of a
counting quasimorphism on elements of the group.

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