過去の記録

過去の記録 ~08/18本日 08/19 | 今後の予定 08/20~

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
渡部真樹 氏 (東京大学大学院数理科学研究科)
Schubert加群の構造とSchubert加群によるfiltrationについて (JAPANESE)
[ 講演概要 ]
Schubert多項式を研究する道具の1つとして, KraskiewiczとPragaczによって 導入されたSchubert加群があります.
今回の発表では, Schubert加群の構造に関する新しい結果と, そこから得られる, 与えられた加群がSchubert加群によるfiltrationを持つ条件について話します.
また, この研究のもともとの動機はSchubert多項式に関するある問題を考えていたことなので, それについても話す予定です.

2014年05月22日(木)

幾何コロキウム

10:00-11:30   数理科学研究科棟(駒場) 122号室
開始時間と開催場所などは変更されることがあるので, セミナーごとにご確認ください.
Boris Hasselblatt 氏 (Tufts Univ)
Godbillon-Vey invariants for maximal isotropic foliations (ENGLISH)
[ 講演概要 ]
The combination of a contact structure and an orientable maximal isotropic foliation gives rise to m+1 Godbillon-Vey invariants for an m+1-dimensional maximal isotropic foliation that are of interest with respect to geometric rigidity: by studying these jointly, we give new proofs of famous "rigidity'' results from the 1980s that require only a very few simple lines of reasoning rather than the elaborate original proofs.

2014年05月21日(水)

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
Shenghao Sun 氏 (Mathematical Sciences Center of Tsinghua University)
Parity of Betti numbers in étale cohomology (ENGLISH)
[ 講演概要 ]
By Hodge symmetry, the Betti numbers of a complex projective smooth variety in odd degrees are even. When the base field has characteristic p, Deligne proved the hard Lefschetz theorem in etale cohomology, and the parity result follows from this. Suh has generalized this to proper smooth varieties in characteristic p, using crystalline cohomology.
The purity of intersection cohomology group of proper varieties suggests that the same parity property should hold for these groups in characteristic p. We proved this by investigating the symmetry in the categorical level.
In particular, we reproved Suh's result, using merely etale cohomology. Some related results will be discussed. This is joint work with Weizhe Zheng.

(本講演は「東京北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, Morningside Center of MathematicsとIHESの双方向同時中継で行います.)

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
見村万佐人 氏 (東北大学)
Group approximation in Cayley topology and coarse geometry
part I: coarse embeddings of amenable groups (ENGLISH)

2014年05月20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
黒木 慎太郎 氏 (東京大学大学院数理科学研究科)
An application of torus graphs to characterize torus manifolds
with extended actions (JAPANESE)
[ 講演概要 ]
A torus manifold is a compact, oriented 2n-dimensional T^n-
manifolds with fixed points. This notion is introduced by Hattori and
Masuda as a topological generalization of toric manifolds. For a given
torus manifold, we can define a labelled graph called a torus graph (
this may be regarded as a generalization of some class of GKM graphs).
It is known that the equivariant cohomology ring of some nice class of
torus manifolds can be computed by using a combinatorial data of torus
graphs. In this talk, we study which torus action of torus manifolds can
be extended to a non-abelian compact connected Lie group. To do this, we
introduce root systems of (abstract) torus graphs and characterize
extended actions of torus manifolds. This is a joint work with Mikiya
Masuda.

統計数学セミナー

13:00-14:10   数理科学研究科棟(駒場) 052号室
荻原 哲平 氏 (大阪大学金融・保険教育研究センター)
非同期観測と観測ノイズの存在の下での最尤型推定法 (JAPANESE)
[ 講演概要 ]
高頻度金融時系列データを用いた複数資産の統計解析での問題として, 観測ノイズと観測の非同期性があり, 実現共分散などのシンプルな推定量は 観測ノイズや観測の非同期性の下で深刻なバイアスをもつ. この問題を解決するノンパラメトリック型推定量に関する研究は多くあり, 最尤型推定量に関しても, 観測ノイズと非同期観測をそれぞれ単独で扱っているものとして, Gloter and Jacod (2001), Ogihara and Yoshida (2012)などがある. 本発表では, 先行研究を紹介しながら観測ノイズと非同期観測の両方が存在する時の 最尤型推定量の漸近挙動に関する結果を紹介する.
[ 講演参考URL ]
http://www.sigmath.es.osaka-u.ac.jp/~kamatani/statseminar/2014/02.html

2014年05月19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) 126号室
高山 茂晴 氏 (東京大学)
On degenerations of Ricci-flat Kähler manifolds (JAPANESE)

2014年05月17日(土)

調和解析駒場セミナー

13:30-17:00   数理科学研究科棟(駒場) 128号室
このセミナーは,月に1度程度,不定期に開催されます.
筒井 容平 氏 (東京大学) 13:30-15:00
拡散性を有しない化学物質に対する走化性方程式の有界な解 (JAPANESE)
[ 講演概要 ]
We consider a chemotaxis system with a logarithmic sensitivity and a non-diffusive chemical substance. For some chemotactic sensitivity constants, Ahn and Kang proved the existence of bounded global solutions to the system. An entropy functional was used in their argument to control the cell density by the density of the chemical substance. Our purpose is to show the existence of bounded global solutions for all the chemotactic sensitivity constants. Assuming the smallness on the initial data in some sense, we can get uniform estimates for time. These estimates are used to extend local solutions.
This talk is partially based on joint work with Yoshie Sugiyama (Kyusyu Univ.) and Juan J.L. Vel\\'azquez (Univ. of Bonn).
香川 智修 氏 (東京都市大学) 15:30-17:00
Heat kernel and Schroedinger kernel on the Heisenberg group (JAPANESE)
[ 講演概要 ]
Heisenberg群上のsub-Laplacianに対する熱核およびSchroedinger核の構成について
解説し、熱核とSchroedinger核との関係について論じる。
またHeisenberg群の群演算にパラメータを、極限操作でユークリッド空間になるように入れたときの、熱核やSchrodinger核に極限操作を行ったときの振る舞いについて考察する。
熱核についてはM. W. Wong氏との共同研究である。

2014年05月15日(木)

幾何コロキウム

10:00-11:30   数理科学研究科棟(駒場) 122号室
開始時間と開催場所などは変更されることがあるので, セミナーごとにご確認ください.
只野 誉 氏 (大阪大学)
Gap theorems for compact gradient Sasaki Ricci solitons (JAPANESE)
[ 講演概要 ]
In this talk we give some necessary and sufficient conditions for compact gradient Sasaki-Ricci solitons to be Sasaki-Einstein. Our result may be considered as a Sasaki geometry version of recent works by H. Li, and M. Fern¥'andez-L¥'opez-E. Garc¥'ia-Rio.

講演会

16:30-17:30   数理科学研究科棟(駒場) 050号室
Cédric Villani 氏 (Université de Lyon, Institut Henri Poincaré)
Synthetic theory of Ricci curvature
― When Monge, Riemann and Boltzmann meet ― (ENGLISH)
[ 講演概要 ]
Optimal transport theory, non-Euclidean geometry and statistical physics met fifteen years ago with the discovery that Ricci curvature can be studied quantitatively thanks to entropy and
Monge-Kantorovich transport.
This unexpected encounter was very fruitful, leading to progress in each of these fields.
[ 講演参考URL ]
http://faculty.ms.u-tokyo.ac.jp/Villani.html

FMSPレクチャーズ

16:30-17:30   数理科学研究科棟(駒場) 050号室
Tea: 16:00-16:30 ホワイエにて
Cédric Villani 氏 (Université de Lyon, Institut Henri Poincaré)
Synthetic theory of Ricci curvature ― When Monge, Riemann and Boltzmann meet ― (ENGLISH)
[ 講演参考URL ]
http://faculty.ms.u-tokyo.ac.jp/Villani.html

2014年05月14日(水)

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
Yul Otani 氏 (Univ. Tokyo)
A Supersymmetric model in AQFT (after Buchholz and Grundling) (ENGLISH)

2014年05月13日(火)

解析学火曜セミナー

16:30-18:00   数理科学研究科棟(駒場) 128号室
岡田 靖則 氏 (千葉大学大学院理学研究科)
Ultra-differentiable classes and intersection theorems (JAPANESE)
[ 講演概要 ]
There are two ways to define notions of
ultra-differentiability: one in terms of estimates on derivatives, and
the other in terms of growth properties of Fourier transforms of
suitably localized functions.
In this talk, we study the relation between BMT-classes and
inhomogeneous Gevrey classes, which are examples of such two kinds of
notions of ultra-differentiability.
We also mention intersection theorems on these classes.
This talk is based on a joint work with Otto Liess (Bologna University).

統計数学セミナー

13:00-14:10   数理科学研究科棟(駒場) 052号室
Selma Chaker 氏 (Bank of Canada)
On High Frequency Estimation of the Frictionless Price: The Use of Observed Liquidity Variables (ENGLISH)
[ 講演概要 ]
Observed high-frequency prices are always contaminated with liquidity costs or market microstructure noise. Inspired by the market microstructure literature, I explicitly model this noise and remove it from observed prices to obtain an estimate of the frictionless price. I then formally test whether the prices adjusted for the estimated liquidity costs are either totally or partially free from noise. If the liquidity costs are only partially removed, the residual noise is smaller and closer to an exogenous white noise than the original noise is. To illustrate my approach, I use the adjusted prices to improve volatility estimation in the presence of noise. If the noise is totally absorbed, I show that the sum of squared returns - which would be inconsistent for return variance when based on observed returns - becomes consistent when based on adjusted returns.
[ 講演参考URL ]
http://www.sigmath.es.osaka-u.ac.jp/~kamatani/statseminar/2014/01.html

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
足助 太郎 氏 (東京大学大学院数理科学研究科)
Transverse projective structures of foliations and deformations of the Godbillon-Vey class (JAPANESE)
[ 講演概要 ]
Given a smooth family of foliations, we can define the derivative of the Godbillon-Vey class
with respect to the family. The derivative is known to be represented in terms of the projective
Schwarzians of holonomy maps. In this talk, we will study transverse projective structures
and connections, and show that the derivative is in fact determined by the projective structure
and the family.

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
Ivan Cherednik 氏 (The University of North Carolina at Chapel Hill, RIMS
)
Global q,t-hypergeometric and q-Whittaker functions (ENGLISH)
[ 講演概要 ]
The lectures will be devoted to the new theory of global
difference hypergeometric and Whittaker functions, one of
the major applications of the double affine Hecke algebras
and a breakthrough in the classical harmonic analysis. They
integrate the Ruijsenaars-Macdonald difference QMBP and
"Q-Toda" (any root systems), and are analytic everywhere
("global") with superb asymptotic behavior.

The definition of the global functions was suggested about
14 years ago; it is conceptually different from the definition
Heine gave in 1846, which remained unchanged and unchallenged
since then. Algebraically, the new functions are closer to
Bessel functions than to the classical hypergeometric and
Whittaker functions. The analytic theory of these functions was
completed only recently (the speaker and Jasper Stokman).

The construction is based on DAHA. The global functions are defined
as reproducing kernels of Fourier-DAHA transforms. Their
specializations are Macdonald polynomials, which is a powerful
generalization of the Shintani and Casselman-Shalika p-adic formulas.
If time permits, the connection of the Harish-Chandra theory of global
q-Whittaker functions will be discussed with the Givental-Lee formula
(Gromov-Witten invariants of flag varieties) and its generalizations due

to Braverman and Finkelberg (algebraic theory of affine flag varieties).

2014年05月12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) 126号室
神本 丈 氏 (九州大学)
Resolution of singularities via Newton polyhedra and its application to analysis (JAPANESE)
[ 講演概要 ]
In the 1970s, A. N. Varchenko precisely investigated the leading term of the asymptotic expansion of an oscillatory integral with real analytic phase by using the geometry of the Newton polyhedron of the phase. Since his study, the importance of the resolution of singularities by means of Newton polyhedra has been strongly recognized. The purpose of this talk is to consider studies around this theme and to explain their relationship with some problems in several complex variables.

代数幾何学セミナー

15:30-17:00   数理科学研究科棟(駒場) 122号室
Andrés Daniel Duarte 氏 (Institut de Mathématiques de Toulouse)
Higher Nash blowup on normal toric varieties and a higher order version of Nobile's theorem (ENGLISH)
[ 講演概要 ]
The higher Nash blowup of an algebraic variety replaces singular points with limits of certain vector spaces carrying first or higher order data associated to the variety at non-singular points. In the case of normal toric varieties, the higher Nash blowup has a combinatorial description in terms of the Gröbner fan. This description will allows us to prove a higher version of Nobile's theorem in this context: for a normal toric variety, the higher Nash blowup is an isomorphism if and only if the variety is non-singular. We will also present some further observations coming from computational experiments.

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
Chien-Hong Cho 氏 (National Chung Cheng University)
On the finite difference approximation for blow-up solutions of the nonlinear wave equation (JAPANESE)
[ 講演概要 ]
We consider in this paper the 1-dim nonlinear wave equation $u_{tt}=u_{xx}+u^{1+\\alpha}$ $(\\alpha > 0)$ and its finite difference analogue. It is known that the solutions of the current equation becomes unbounded in finite time, a phenomenon which is often called blow-up. Numerical approaches on such kind of problems are widely investigated in the last decade. However, those results are mainly about parabolic blow-up problems. Compared with the parabolic ones, there is a remarkable property for the solution of the nonlinear wave equation -- the existence of the blow-up curve. That is, even though the solution has become unbounded at certain points, the solution continues to exist at other points and blows up at later times. We are concerned in this paper as to how a finite difference scheme can reproduce such a phenomenon.
[ 講演参考URL ]
http://www.infsup.jp/utnas/

2014年05月08日(木)

幾何コロキウム

10:00-11:30   数理科学研究科棟(駒場) 122号室
開始時間と開催場所などは変更されることがあるので, セミナーごとにご確認ください.
小野 肇 氏 (埼玉大学)
非ハミルトン体積最小なハミルトン安定ラグランジュトーラスについて (JAPANESE)
[ 講演概要 ]
Y. –G. Oh はケーラー多様体内のラグランジュ部分多様体について、ハミルトン変形のもとでの体積の極小性(ハミルトン安定性)や最小性(ハミルトン体積最小性)について考察した。これは等周問題の1つの一般化と考えられ、例えば、複素ユークリッド空間内の標準的トーラスや複素射影空間たちの直積のトーラス軌道などはハミルトン安定であることが知られていた。本講演では次の2つの結果について紹介する:
1. 3次元以上の複素ベクトル空間のほとんどの標準的トーラスはハミルトン体積最小ではない。
2. 3次元以上の任意のコンパクトトーリックケーラー多様体のトーラス軌道にはハミルトン体積最小ではないものが数多く存在する。

2014年05月07日(水)

数理人口学・数理生物学セミナー

14:50-16:20   数理科学研究科棟(駒場) 128号室
江夏洋一 氏 (東京大学大学院数理科学研究科)
感染個体の齢構造を持つ微分方程式系の漸近挙動とその周辺 (JAPANESE)
[ 講演概要 ]
多様化する生命現象を特徴付ける要素の長期継続的な挙動を調べるため,
数理モデリングを用いた定性的な理論構築は広く行われてきた. 本講演では, 感
受性個体, 感染個体, 回復個体等の数を変数とする感染症モデルの正値解の漸近
挙動に関する成果を報告し, 基本再生産数を用いた感染症の終局的流行規模の変
化を議論する. 特に, Magal, McCluskey, Webb (2010) によって定式化された感
染個体の齢構造 (感染齢) を含む SIR 感染症モデルにおいて, 感染伝達パラメ
ータが感染齢について単調増加である場合, 感染齢を持つ方程式系から離散的・
連続的な遅れをもつ微分方程式系を得ることが出来たアイデアを新たに紹介した
い. Lyapunov 汎関数法, 単調反復法や感染平衡解の周りでの線形化方程式系に
対する固有値解析をはじめとする遅延方程式系に対する近年の解析手法の応用事
例についても, 感染症モデルや糖尿病モデルなどと共に報告する.탞

2014年05月02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
旧記録は、上記セミナーURLにあります。
お茶&Coffee&お菓子: 16:00~16:30 (コモンルーム)。

A.P. Veselov 氏 (Loughborough, UK and Tokyo, Japan)
From hyperplane arrangements to Deligne-Mumford moduli spaces: Kohno-Drinfeld way (ENGLISH)
[ 講演概要 ]
Gaudin subalgebras are abelian Lie subalgebras of maximal
dimension spanned by generators of the Kohno-Drinfeld Lie algebra t_n,
associated to A-type hyperplane arrangement.
It turns out that Gaudin subalgebras form a smooth algebraic variety
isomorphic to the Deligne-Mumford moduli space \\bar M_{0,n+1} of
stable genus zero curves with n+1 marked points.
A real version of this result allows to describe the
moduli space of integrable n-dimensional tops and
separation coordinates on the unit sphere
in terms of the geometry of Stasheff polytope.

The talk is based on joint works with L. Aguirre and G. Felder and with K.
Schoebel.

2014年04月30日(水)

代数学コロキウム

16:40-17:40   数理科学研究科棟(駒場) 056号室
丸山拓也 氏 (東京大学数理科学研究科)
An effective upper bound for the number of principally polarized Abelian schemes (JAPANESE)

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
小沢登高 氏 (京大数理研)
Noncommutative real algebraic geometry of Kazhdan's property (T) (ENGLISH)

2014年04月28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
斎藤俊輔 氏 (東大数理)
On the existence problem of Kähler-Ricci solitons (JAPANESE)

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