過去の記録

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

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)

A higher rank version of Abel-Jacobi's theorem (Room 056)
[ 講演概要 ]

(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

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

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

[ 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)

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

[ 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

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

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

Easy full-joint estimators of stable processes
[ 講演概要 ]

[ 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

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

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
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.

2007年07月09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

Geometry of hyperkahler quotients

2007年07月06日(金)

統計数学セミナー

15:00-16:10   数理科学研究科棟(駒場) 122号室
Arturo KOHATSU-HIGA 氏 (大阪大学大学院基礎工学研究科)
Estimating multidimensional densities through the Malliavin-Thalmaier formula
[ 講演概要 ]
TBA
[ 講演参考URL ]
http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2007/03.html

2007年07月05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
Rolf Dyre Svegstrup 氏 (東大数理)
Factorization in $C^*$-Algebras

2007年07月04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
Lars Diening 氏 (Universitat Freiburg)
The Lipschitz truncation method
[ 講演概要 ]
We study the existence of weak solutions to the incompressible $p$-Navier Stokes equations. This system can be used to describe the flow of honey, ketchup, blood, suspensions, polymers, and glaciers. We are interested in small values of $p$, where the method of monotone operators fails. We establish weak solutions by means of the Lipschitz truncation technique, where Sobolev Functions are approximated by Lipschitz functions in a special way. We apply the technique also to electrorheological fluids, where the exponent $p$ depends on the electric field.
[ 講演参考URL ]
http://coe.math.sci.hokudai.ac.jp/sympo/pde_ra/index.html

東京幾何セミナー

14:40-18:00   数理科学研究科棟(駒場) 056号室

「今後の予定」欄には、東工大で行われるセミナーは表��

A Special Lagrangian Fibration in the TAUB-NUT Space
[ 講演概要 ]
この講演では, Taub-NUT space における special Lagrangian fibration の具体的構成について述べるつもりである.Taub-NUT space は複素多様体としては二次元複素空間であるが,計量が通常と異なり完備で非平坦なリッチ平坦計量をもつ Hyper-Kahler 多様体として特徴づけられる.この空間の special Lagrangian fibration が,Ionel-Min Oo の手法を用いることで具体的に構成できることを見る.

Symmetries in generalized complex geometry
[ 講演概要 ]