過去の記録

過去の記録 ~02/21本日 02/22 | 今後の予定 02/23~

2015年09月25日(金)

談話会・数理科学講演会

16:50-17:50   数理科学研究科棟(駒場) 大講義室号室
Gerhard Huisken 氏 (The Mathematisches Forschungsinstitut Oberwolfach )
Mean curvature flow with surgery
[ 講演概要 ]
We study the motion of hypersurfaces in a Riemannian manifold
with normal velocity equal to the mean curvature of the
evolving hypersurface. In general this quasilinear, parabolic
evolution system may have complicated singularities in finite time.
However, under natural assumptions such as embeddedness of the surface
and positivity of the mean curvature (case of 2-dimensional surfaces)
all singularities can be classified and developing "necks" can be
removed by a surgery procedure similar to techniques employed
by Hamilton and Perelman in the Ricci-flow of Riemannian metrics.
The lecture describes results and techniques for mean curvature flow
with surgery developed in joint work with C. Sinestrari and S. Brendle.
[ 講演参考URL ]
http://www.mfo.de/about-the-institute/staff/prof.-dr.-gerhard-huisken

古典解析セミナー

16:00-17:00   数理科学研究科棟(駒場) 126号室
Damiran Tseveennamjil 氏 (モンゴル生命科学大学)
Twistor理論からみた一般Schlesinger系の合流 (JAPANESE)
[ 講演概要 ]
Grassmann多様体上の一般超幾何関数に対する合流の操作の類似として、一般Schlesinger系を導く線形方程式系の合流を論じる。

2015年09月17日(木)

統計数学セミナー

15:00-16:10   数理科学研究科棟(駒場) 052号室
Stefano Iacus 氏 (University of Milan)
The use of S4 classes and methods in the Yuima R package
[ 講演概要 ]
In this talk we present the basic concept of S4 classes and methods approach for object oriented programming in R. As a working example, we introduce the structure of the Yuima package for simulation and inference of stochastic differential equations. We will describe the basic classes and objects as well as some recent extensions which allows for Carma and Co-Garch processes handling in Yuima.

東京無限可積分系セミナー

14:00-15:30   数理科学研究科棟(駒場) 002号室
Simon Wood 氏 (The Australian National University)
Classifying simple modules at admissible levels through
symmetric polynomials (ENGLISH)
[ 講演概要 ]
From infinite dimensional Lie algebras such as the Virasoro
algebra or affine Lie (super)algebras one can construct universal
vertex operator algebras. These vertex operator algebras are simple at
generic central charges or levels and only contain proper ideals at so
called admissible levels. The simple quotient vertex operator algebras
at these admissible levels are called minimal model algebras. In this
talk I will present free field realisations of the universal vertex
operator algebras and show how they allow one to elegantly classify
the simple modules over the simple quotient vertex operator algebras
by using a deep connection to symmetric polynomials.

2015年09月11日(金)

FMSPレクチャーズ

17:00-18:30   数理科学研究科棟(駒場) 126号室
Alexander Voronov 氏 (Univ. of Minnesota)
Operads and their applications to Mathematical Physics (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Voronov.pdf

2015年09月10日(木)

FMSPレクチャーズ

17:00-18:30   数理科学研究科棟(駒場) 126号室
Alexander Voronov 氏 (Univ. of Minnesota)
Operads and their applications to Mathematical Physics (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Voronov.pdf

FMSPレクチャーズ

15:30-16:30   数理科学研究科棟(駒場) 056号室
Zhi Chen 氏 (Hefei University of Technology)
Lifting of maps between surfaces (ENGLISH)
[ 講演概要 ]
The Thom conjecture says the algebraic curves have minimal genus among those surfaces Imbedded in CP^2 having fixed degree. This conjecture was solved by Kronheimer and Mrowka by using Seiberg-Witten invariants. In this talk we try to understand the content of this conjecture. We will construct these imbedded surface with minimal genus explicitly, and present some kind of generalization of this conjecture.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_ZhiChen.pdf

2015年09月09日(水)

代数学コロキウム

17:00-18:00   数理科学研究科棟(駒場) 056号室
Emmanuel Ullmo 氏 (IHES)
The hyperbolic Ax-Lindemann conjecture (English)
[ 講演概要 ]
The hyperbolic Ax Lindemann conjecture is a functional transcendental statement which describes the Zariski closure of "algebraic flows" on Shimura varieties. We will describe the proof of this conjecture and its consequences for the André-Oort conjecture. This is a joint work with Bruno Klingler and Andrei Yafaev.

2015年09月08日(火)

諸分野のための数学研究会

10:30-11:30   数理科学研究科棟(駒場) 056号室
Monika Muszkieta 氏 (Wroclaw University of Technology)
Duality based approaches to total variation-like flows with applications to image processing (English)
[ 講演概要 ]
During the last years, total variation models have became very popular in image processing and analysis. They have been used to solve such problems as image restoration, image deblurring or image inpainting. Their interesting and successful applications became the motivation for many authors to rigorous analysis of properties of solutions to the corresponding total variation flows. The main difficulty in numerical approximation of solutions to these flows is caused by the lack of di fferentiability of the total variation term, and the commonly used approach to overcome this difficulty consists in considering of the dual formulation. In the talk, we consider two total variation flow models. The first one is the anisotropic total variation flow on $L^2$ with additional regularization, and the second one, is the total variation flow on $H^{-s}$. We introduce duality based numerical schemes for approximate solutions to corresponding equations and present some applications to image processing.
This talk is based on joint work with Y. Giga, P. Mucha and P. Rybka.

解析学火曜セミナー

16:50-18:20   数理科学研究科棟(駒場) 126号室
水谷治哉 氏 (大阪大学・理学研究科)
長距離型斥力ポテンシャルを持つシュレディンガー方程式の時間大域的ストリッカーツ評価 (Japanese)
[ 講演概要 ]
We will discuss a resent result on global-in-time Strichartz estimates for Schr\"odinger equations with slowly decreasing repulsive potentials. If the potential is of very short-range type, there is a simple method due to Rodnianski-Schlag or Burq et al, which seems to be difficult to apply for the present case. The proof instead follows a similar line as in speaker’s resent joint work with J.-M. Bouclet. In particular, we employ both Morawetz type estimates and the methods of micro local analysis such as the Isozaki-Kitada parametrix, even in the low frequency regime.

2015年09月02日(水)

FMSPレクチャーズ

17:00-18:30   数理科学研究科棟(駒場) 126号室
Alexander Voronov 氏 (Univ. of Minnesota)
Operads and their applications to Mathematical Physics (ENGLISH)
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Voronov.pdf

2015年08月31日(月)

博士論文発表会

16:30-17:45   数理科学研究科棟(駒場) 128号室
藤城 謙一 氏 (東京大学大学院数理科学研究科)
Approximate Controllability, Non-homogeneous Boundary Value Problems and Inverse Source Problems for Fractional Diffusion Equations(非整数階拡散方程式に対する近似可制御性、非斉次境界値問題およびソース項決定逆問題) (JAPANESE)

2015年08月28日(金)

談話会・数理科学講演会

16:50-17:50   数理科学研究科棟(駒場) 002号室
Athanase Papadopoulos 氏 (Institut de Recherche Mathématique Avancée, Université de Strasbourg et CNRS)
On the development of Riemann surfaces and moduli (ENGLISH)
[ 講演概要 ]
I will describe a selection of major fundamental ideas in the theory
of Riemann surfaces and moduli, starting from the work of Riemann, and
ending with recent works.

2015年08月07日(金)

統計数学セミナー

14:40-15:50   数理科学研究科棟(駒場) 052号室
生方雅人 氏 (釧路公立大学)
Effectiveness of time-varying minimum value at risk and expected shortfall hedging
[ 講演概要 ]
This paper assesses the incremental value of time-varying minimum value at risk (VaR) and expected shortfall (ES) hedging strategies over unconditional hedging strategy. The conditional futures hedge ratios are calculated through estimation of multivariate volatility models under a skewed and leptokurtic distribution and Monte Carlo simulation for conditional skewness and kurtosis of hedged portfolio returns. We examine DCC-GJR models with or without encompassing realized covariance measure (RCM) from high-frequency data under a multivariate skewed Student's t-distribution. In the out-of-sample analysis with a daily rebalancing approach, the empirical results show that the conditional minimum VaR and ES hedging strategies outperform the unconditional hedging strategy. We find that the use of RCM improves the futures hedging performance for a short hedge, although the degree of improvement is small relative to that when switching from unconditional to conditional.

統計数学セミナー

13:20-14:30   数理科学研究科棟(駒場) 052号室
Yoann Potiron 氏 (University of Chicago)
ESTIMATION OF INTEGRATED QUADRATIC COVARIATION BETWEEN TWO ASSETS WITH ENDOGENOUS SAMPLING TIMES
[ 講演概要 ]
When estimating integrated covariation between two assets based on high-frequency data,simple assumptions are usually imposed on the relationship between the price processes and the observation times. In this paper, we introduce an endogenous 2-dimensional model and show that it is more general than the existing endogenous models of the literature. In addition, we establish a central limit theorem for the Hayashi-Yoshida estimator in this general endogenous model in the case where prices follow pure-diffusion processes.

2015年07月30日(木)

博士論文発表会

10:30-11:45   数理科学研究科棟(駒場) 128号室
飛澤 和則 氏 (東京大学大学院数理科学研究科)
Theory and application of a meta lambda calculus with cross-level computation (レベル横断的計算機構を持つメタラムダ計算の理論と応用) (JAPANESE)

2015年07月29日(水)

博士論文発表会

16:00-17:15   数理科学研究科棟(駒場) 128号室
鈴木 航介 氏 (東京大学大学院数里科学研究科)
Accelerating convergence and tractability of multivariate numerical integration when the L1-norms of the higher order derivatives of the integrand grow at most exponentially(被積分関数の高階偏微分のL1ノルムの増大度が高々指数的である場合の多次元数値積分の加速的な収束と計算容易性) (JAPANESE)

博士論文発表会

17:30-18:45   数理科学研究科棟(駒場) 128号室
芳木 武仁 氏 (東京大学大学院数理科学研究科)
Research on Walsh figure of merit for higher order convergent Quasi-Monte Carlo integration(高次収束準モンテカルロ積分のためのWalsh figure of meritの研究) (JAPANESE)

2015年07月28日(火)

講演会

17:00-18:00   数理科学研究科棟(駒場) 056号室
Vincent Alberge 氏 (Université de Strasbourg)
Convergence of some horocyclic deformations to the Gardiner-Masur
boundary of Teichmueller space. (ENGLISH)
[ 講演概要 ]
It is well known that a point of the Teichmueller space and a measured foliation determine an isometric embedding of the hyperbolic disc to the Teichmueller space equipped with the so-called Teichmueller metric. In this talk, we will consider the image by this embedding of a particular horocycle whose points will be called an horocyclic deformation. To be more precise, we will be interested in the closure of this subset in the Gardiner-Masur compactification. As the embedding of the disc does not admit a continuous extension to boundaries, we cannot say that the boundary of the set of horocyclic deformations consists of one point.
However, according to Miyachi's results, we will see that it is the case if the given foliation is either a simple closed curve or a uniquely ergodic foliation.

Lie群論・表現論セミナー

17:00-18:30   数理科学研究科棟(駒場) 122号室
Fabian Januszewski 氏 (Karlsruhe Institute of Technology)
On g,K-modules over arbitrary fields and applications to special values of L-functions
[ 講演概要 ]
I will introduce g,K-modules over arbitrary fields of characteristic 0 and discuss their fundamental properties and constructions, including Zuckerman functors. This may be applied to produce models of certain standard modules over number fields, which has applications to special values of automorphic L-functions, and also furnishes the space of regular algebraic cusp forms of GL(n) with a natural global Q-structure.

2015年07月27日(月)

東京確率論セミナー

16:50-18:20   数理科学研究科棟(駒場) 128号室
鈴木 康平 氏 (京都大学大学院理学研究科)
Convergence of Brownian motions on RCD*(K,N) spaces
[ 講演概要 ]
RCD*(K,N)空間とは, Erbar-Kuwada-Sturmによって導入された測度距離空間のクラスで, 「次元N以下, Ricci曲率K以上」という概念を測度距離空間上に一般化した概念である. RCD*(K,N)空間上では, Cheeger energyから定まるDirichle形式が正則になることが知られており, 対応するMarkov過程は, Brown運動と呼ばれる. 本講演では, RCD*(K,N)空間で直径D以下という条件の下, 「 空間がmeasured Gromov-Hausdorff収束する」ことと,「 Brown運動が収束する」ことが同値であることを示す.

2015年07月24日(金)

作用素環セミナー

16:45-18:15   数理科学研究科棟(駒場) 122号室
Mikael Pichot 氏 (McGill Univ.)
Applications of Boltzmann's S=k log W in algebra and analysis

幾何コロキウム

10:00-11:30   数理科学研究科棟(駒場) 126号室
高津飛鳥 氏 (首都大学東京)
High-dimensional metric-measure limit of Stiefel manifolds (Japanese)
[ 講演概要 ]
A metric measure space is the triple of a complete separable metric space with a Borel measure on this space. Gromov defined a concept of convergence of metric measure spaces by the convergence of the sets of 1-Lipschitz functions on the spaces. We study and specify the high-dimensional limit of Stiefel manifolds in the sense of this convergence; the limit is the infinite-dimensional Gaussian space, which is drastically different from the manifolds. This is a joint work with Takashi SHIOYA (Tohoku univ).

FMSPレクチャーズ

16:00-19:00   数理科学研究科棟(駒場) 268号室
Fikret Golgeleyen 氏 (Bulent Ecevit University)
Solvability and approximate solution of a coefficient inverse problem for the kinetic equation (ENGLISH)
[ 講演概要 ]
The existence, uniqueness and stability of the solution of a coefficient inverse problem for the kinetic equation are proven.
The approximate solution of the problem in one-dimensional case is investigated by using two different techniques: finite difference approximation (FDA) and symbolic computation approach (SCA).
A comparison among the exact solution of the problem, the numerical solution obtained from FDA and the approximate analytical solution obtained from SCA is presented.
[ 講演参考URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Fikret.pdf

2015年07月23日(木)

代数学コロキウム

13:00-16:30   数理科学研究科棟(駒場) 056号室
Lasse Grimmelt 氏 (ゲッティンゲン大学/早稲田大学) 13:00-14:00
Representation of squares by cubic forms - Estimates for the appearing exponential sums (English)
Haoyu Hu 氏 (東京大学数理科学研究科) 14:15-15:15
Ramification and nearby cycles for $\ell$-adic sheaves on relative curves (English)
[ 講演概要 ]
I will present a new approach for a formula of Deligne and Kato that computes the dimension of the nearby cycle complex of an $\ell$-adic sheaf on a smooth relative curve over a strictly henselian trait such that $p$ is not one of its uniformizer. Deligne considered the case where the sheaf has no vertical ramification and Kato extended the formula to the general case. My approach is based on ramification theory of Abbes and Saito. It computes the nearby cycle complex in terms of the refined Swan conductor. In fact, I compare Abbes-Saito's refined Swan conductor with Kato's Swan conductor with differential values, which is the key ingredient in Kato's formula; the case of rank one sheaves is due to Abbes and Saito. My approach provides also a new independent proof of Deligne-Kato's formula.
若林 泰央 氏 (東京大学数理科学研究科) 15:30-16:30
Explicit computation of the number of dormant opers and duality (Japanese)

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