Text only print
Full screen print
Seminar information archive
Seminar information archive ～05/21｜Today's seminar 05/22 | Future seminars 05/23～
Colloquium
16:30-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
平地健吾 (東京大学大学院数理科学研究科)
What is Q-curvature?
次回開催日は11月28日(金)(講演者:川又雄二郎 氏)です。ご注意下さい。
平地健吾 (東京大学大学院数理科学研究科)
What is Q-curvature?
[ Abstract ]
共形幾何は次元の偶奇におうじて著しく異なった性質をもちます。その多くは n次元球面の共形自己同型群SO(n+1,1)が奇数次元ならB型,偶数次元ならD型になるといことから説明できます。この講演では偶数次元にのみ現れるQ-曲率とよばれる局所不変量とその周辺に現れる共形不変量および不変作用素の理論を紹介します。Q-曲率はAdS/CFT対応にも自然に現れることもあり,最近の共形幾何の主要テーマになっていますが,その定義は簡単ではありません。Q-曲率の(短い)歴史と表現論の結果をふまえて,なっとくのできる定義を与えることを目指します。
[ Reference URL ]共形幾何は次元の偶奇におうじて著しく異なった性質をもちます。その多くは n次元球面の共形自己同型群SO(n+1,1)が奇数次元ならB型,偶数次元ならD型になるといことから説明できます。この講演では偶数次元にのみ現れるQ-曲率とよばれる局所不変量とその周辺に現れる共形不変量および不変作用素の理論を紹介します。Q-曲率はAdS/CFT対応にも自然に現れることもあり,最近の共形幾何の主要テーマになっていますが,その定義は簡単ではありません。Q-曲率の(短い)歴史と表現論の結果をふまえて,なっとくのできる定義を与えることを目指します。
次回開催日は11月28日(金)(講演者:川又雄二郎 氏)です。ご注意下さい。
2008/11/20
Applied Analysis
16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
Jan Haskovec
(Vienna University of Technology(オーストリア))
Stochastic Particle Approximation for Measure Valued Solutions of the 2D Keller-Segel System
Jan Haskovec
(Vienna University of Technology(オーストリア))
Stochastic Particle Approximation for Measure Valued Solutions of the 2D Keller-Segel System
[ Abstract ]
We construct an approximation to the measure valued, global in time solutions to the Keller-Segel model in 2D, based on systems of stochastic interacting particles. The advantage of our approach is that it reproduces the well-known dichtomy in the qualitative behavior of the system and, moreover, captures the solution even after the possible blow-up events. We present a numerical method based on this approach and show some numerical results. Moreover, we make a first step toward the convergence analysis of our scheme by proving the convergence of the stochastic particle approximation for the Keller-Segel model with a regularized interaction potential. The proof is based on a BBGKY-like approach for the corresponding particle distribution function.
We construct an approximation to the measure valued, global in time solutions to the Keller-Segel model in 2D, based on systems of stochastic interacting particles. The advantage of our approach is that it reproduces the well-known dichtomy in the qualitative behavior of the system and, moreover, captures the solution even after the possible blow-up events. We present a numerical method based on this approach and show some numerical results. Moreover, we make a first step toward the convergence analysis of our scheme by proving the convergence of the stochastic particle approximation for the Keller-Segel model with a regularized interaction potential. The proof is based on a BBGKY-like approach for the corresponding particle distribution function.
2008/11/19
Number Theory Seminar
16:30-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Olivier Fouquet (大阪大学)
Dihedral Iwasawa theory of ordinary modular forms
Olivier Fouquet (大阪大学)
Dihedral Iwasawa theory of ordinary modular forms
[ Abstract ]
According to Hida theory, the Galois representation attached to a nearly-ordinary Hilbert eigencuspform belongs to a p-adic analytic family of Galois representations parametrized by varying weights. After restricting it to the absolute Galois group of a quadratic totally complex extension, it also belongs to a p-adic family coming from classical dihedral Iwasawa theory. We will explain the proofs of part of the main conjecture in Iwasawa theory in these situations, i.e divisibilities of characteristic ideals when equalities are actually expected.
According to Hida theory, the Galois representation attached to a nearly-ordinary Hilbert eigencuspform belongs to a p-adic analytic family of Galois representations parametrized by varying weights. After restricting it to the absolute Galois group of a quadratic totally complex extension, it also belongs to a p-adic family coming from classical dihedral Iwasawa theory. We will explain the proofs of part of the main conjecture in Iwasawa theory in these situations, i.e divisibilities of characteristic ideals when equalities are actually expected.
2008/11/18
Lie Groups and Representation Theory
16:30-18:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Jorge Vargas (FAMAF-CIEM, C\'ordoba)
Liouville measures and multiplicity formulae for admissible restriction of Discrete Series
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html
Jorge Vargas (FAMAF-CIEM, C\'ordoba)
Liouville measures and multiplicity formulae for admissible restriction of Discrete Series
[ Abstract ]
Let $H \\subset G$ be reductive matrix Lie groups. We fix a square integrable irreducible representation $\\pi$ of $G.$
Let $\\Omega $ denote the coadjoint orbit of the Harish-Chandra parameter of $\\pi.$
Assume $\\pi$ restricted to $H$ is admissible. In joint work with Michel Duflo, by means of "discrete" and "continuos" Heaviside functions we relate the multiplicity of each irreducible $H-$factor of $\\pi$ restricted to $H$ and push forward to $\\mathfrak h^\\star$ of the Liouville measure for $\\Omega.$ This generalizes work of Duflo-Heckman-Vergne.
[ Reference URL ]Let $H \\subset G$ be reductive matrix Lie groups. We fix a square integrable irreducible representation $\\pi$ of $G.$
Let $\\Omega $ denote the coadjoint orbit of the Harish-Chandra parameter of $\\pi.$
Assume $\\pi$ restricted to $H$ is admissible. In joint work with Michel Duflo, by means of "discrete" and "continuos" Heaviside functions we relate the multiplicity of each irreducible $H-$factor of $\\pi$ restricted to $H$ and push forward to $\\mathfrak h^\\star$ of the Liouville measure for $\\Omega.$ This generalizes work of Duflo-Heckman-Vergne.
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html
Tuesday Seminar on Topology
17:00-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
宍倉 光広 (京都大学大学院理学研究科)
複素力学系のくりこみと剛性
宍倉 光広 (京都大学大学院理学研究科)
複素力学系のくりこみと剛性
[ Abstract ]
無限に分岐が集積しているような
ある種の力学系においては、相空間やパラメータ空間の
微細構造が取り上げる個々の力学系の族に寄らない
普遍的構造をもったりすることが知られており、
ある意味で剛性の問題とつながっている。この現象の説明には、
ある部分集合への再帰写像の構成から得られる、あるクラスの
力学系全体の空間で定義されるメタ力学系としての
くりこみ作用素の考え方が重要である。これに関して、
講演者と稲生啓行による中立的不動点をもつ複素力学系の
近放物型くりこみの話を中心に解説する。
無限に分岐が集積しているような
ある種の力学系においては、相空間やパラメータ空間の
微細構造が取り上げる個々の力学系の族に寄らない
普遍的構造をもったりすることが知られており、
ある意味で剛性の問題とつながっている。この現象の説明には、
ある部分集合への再帰写像の構成から得られる、あるクラスの
力学系全体の空間で定義されるメタ力学系としての
くりこみ作用素の考え方が重要である。これに関して、
講演者と稲生啓行による中立的不動点をもつ複素力学系の
近放物型くりこみの話を中心に解説する。
2008/11/17
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
野沢 啓 (東大数理)
Deformation of Sasakian metrics
野沢 啓 (東大数理)
Deformation of Sasakian metrics
2008/11/14
Lecture Series on Mathematical Sciences in Soceity
16:20-17:50 Room #128 (Graduate School of Math. Sci. Bldg.)
中川 淳一 (新日本製鐵先端技術研究所)
製鐵プロセスの数学Ⅰ
中川 淳一 (新日本製鐵先端技術研究所)
製鐵プロセスの数学Ⅰ
2008/11/13
Applied Analysis
16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
杉山 由恵 (津田塾大学・学芸学部・数学科)
Aronson-Benilan type estimate and the optimal Hoelder continuity of weak solutions for the 1D degenerate Keller-Segel systems
杉山 由恵 (津田塾大学・学芸学部・数学科)
Aronson-Benilan type estimate and the optimal Hoelder continuity of weak solutions for the 1D degenerate Keller-Segel systems
[ Abstract ]
We consider the Cauchy problem for the 1D Keller-Segel system of degenerate
type (KS)_m with $m>1$:
u_t= \\partial_x^2 u^m - \\partial_x (u^{q-2} \\partial_x v),
-\\partial_x^2 v + v - u=0.
We establish a uniform estimate from below of $\\partial_x^2 u^{m-1}$.
The corresponding estimate to the porous medium equation is well-known
as an Aronson-Benilan type.
As an application of our Aronson-Benilan type estimate,
we prove the optimal Hoelder continuity of the weak solution $u$ of (KS)_m.
In addition, we find that the positive region $D(t):=\\{x \\in \\R; u(x,t)>0\\}$
of $u$ is monotonically non-decreasing with respect to the time $t$.
We consider the Cauchy problem for the 1D Keller-Segel system of degenerate
type (KS)_m with $m>1$:
u_t= \\partial_x^2 u^m - \\partial_x (u^{q-2} \\partial_x v),
-\\partial_x^2 v + v - u=0.
We establish a uniform estimate from below of $\\partial_x^2 u^{m-1}$.
The corresponding estimate to the porous medium equation is well-known
as an Aronson-Benilan type.
As an application of our Aronson-Benilan type estimate,
we prove the optimal Hoelder continuity of the weak solution $u$ of (KS)_m.
In addition, we find that the positive region $D(t):=\\{x \\in \\R; u(x,t)>0\\}$
of $u$ is monotonically non-decreasing with respect to the time $t$.
Operator Algebra Seminars
16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Mikael Pichot (IPMU)
Groups of friezes and property RD
Mikael Pichot (IPMU)
Groups of friezes and property RD
2008/11/11
Tuesday Seminar of Analysis
16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)
新國 裕昭 (首都大学東京)
Rotation number approach to spectral analysis of the generalized Kronig-Penney Hamiltonians
新國 裕昭 (首都大学東京)
Rotation number approach to spectral analysis of the generalized Kronig-Penney Hamiltonians
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Thomas Andrew Putman (MIT)
The second rational homology group of the moduli space of curves
with level structures
Thomas Andrew Putman (MIT)
The second rational homology group of the moduli space of curves
with level structures
[ Abstract ]
Let $\\Gamma$ be a finite-index subgroup of the mapping class
group of a closed genus $g$ surface that contains the Torelli group. For
instance, $\\Gamma$ can be the level $L$ subgroup or the spin mapping class
group. We show that $H_2(\\Gamma;\\Q) \\cong \\Q$ for $g \\geq 5$. A corollary
of this is that the rational Picard groups of the associated finite covers
of the moduli space of curves are equal to $\\Q$. We also prove analogous
results for surface with punctures and boundary components.
Let $\\Gamma$ be a finite-index subgroup of the mapping class
group of a closed genus $g$ surface that contains the Torelli group. For
instance, $\\Gamma$ can be the level $L$ subgroup or the spin mapping class
group. We show that $H_2(\\Gamma;\\Q) \\cong \\Q$ for $g \\geq 5$. A corollary
of this is that the rational Picard groups of the associated finite covers
of the moduli space of curves are equal to $\\Q$. We also prove analogous
results for surface with punctures and boundary components.
2008/11/10
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
川口 周 (阪大理)
射影空間の射に関する高さ関数の力学系的性質
川口 周 (阪大理)
射影空間の射に関する高さ関数の力学系的性質
2008/11/07
Lecture Series on Mathematical Sciences in Soceity
16:20-17:50 Room #128 (Graduate School of Math. Sci. Bldg.)
大本 隆 (野村證券金融工学研究センター)
デリバティブ・プロダクツの価格付け I
大本 隆 (野村證券金融工学研究センター)
デリバティブ・プロダクツの価格付け I
Algebraic Geometry Seminar
16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)
Misha Verbitsky (ITEP and IPMU)
Hyperkaehler SYZ conjecture and stability
Misha Verbitsky (ITEP and IPMU)
Hyperkaehler SYZ conjecture and stability
[ Abstract ]
Let L be a nef bundle on a hyperkaehler manifold. A Hyperkaehler SYZ conjecture postulates that L is semi-ample. As shown by Matsushita, this implies existence of holomorphic Lagrangian fibrations on hyperkaehler manifolds. It was conjectured by many
people, most recently by Tschinkel, Hassett, Huybrechts and Sawon. We prove that a sufficiently big power of L is effective, assuming that L admits a semi-positive metric. A multiplier ideal version of this argument would give effectivity of L^N for any nef L. The proof uses stability and Boucksom's divisorial
Zariski decomposition.
Let L be a nef bundle on a hyperkaehler manifold. A Hyperkaehler SYZ conjecture postulates that L is semi-ample. As shown by Matsushita, this implies existence of holomorphic Lagrangian fibrations on hyperkaehler manifolds. It was conjectured by many
people, most recently by Tschinkel, Hassett, Huybrechts and Sawon. We prove that a sufficiently big power of L is effective, assuming that L admits a semi-positive metric. A multiplier ideal version of this argument would give effectivity of L^N for any nef L. The proof uses stability and Boucksom's divisorial
Zariski decomposition.
2008/11/05
Geometry Seminar
14:45-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)
二木昌宏 (東京大学大学院数理科学研究科) 14:45-16:15
Directed Fukaya category の安定化について
四元数ケーラー構造の剛性定理
二木昌宏 (東京大学大学院数理科学研究科) 14:45-16:15
Directed Fukaya category の安定化について
[ Abstract ]
有向深谷圏(Directed Fukaya category)はホモロジー的ミラー対称性を Fano 多様体に拡張する目的で Kontsevich により提案され,Seidel により定式化された.これはシンプレクティック多様体の深谷圏の類似であり,exact Lefschetz fibration に対して定義される.有向深谷圏には幾つかの計算可能な例が知られているが,その構造については分かっていないことが多い.本講演では有向深谷圏の定義から始め,exact Lefschetz fibration の安定化(stabilization)と言われる操作での挙動に関する研究について報告する.Auroux-Katzarkov-Orlov の研究との関係にも触れる予定である.
服部広大 (東京大学大学院数理科学研究科) 16:30-18:00有向深谷圏(Directed Fukaya category)はホモロジー的ミラー対称性を Fano 多様体に拡張する目的で Kontsevich により提案され,Seidel により定式化された.これはシンプレクティック多様体の深谷圏の類似であり,exact Lefschetz fibration に対して定義される.有向深谷圏には幾つかの計算可能な例が知られているが,その構造については分かっていないことが多い.本講演では有向深谷圏の定義から始め,exact Lefschetz fibration の安定化(stabilization)と言われる操作での挙動に関する研究について報告する.Auroux-Katzarkov-Orlov の研究との関係にも触れる予定である.
四元数ケーラー構造の剛性定理
[ Abstract ]
四元数ケーラー構造とは,特殊なホロノミー群をもつリーマン計量の一種である.コンパクト多様体上では,四元数ケーラー構造の非自明な変形が存在しないこと(剛性定理)が,ツイスター理論を用いることで証明されている.今回は,ツイスター理論を使わない剛性定理の証明について説明する.
四元数ケーラー構造とは,特殊なホロノミー群をもつリーマン計量の一種である.コンパクト多様体上では,四元数ケーラー構造の非自明な変形が存在しないこと(剛性定理)が,ツイスター理論を用いることで証明されている.今回は,ツイスター理論を使わない剛性定理の証明について説明する.
2008/11/04
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Misha Verbitsky (ITEP, Moscow)
Lefschetz SL(2)-action and cohomology of Kaehler manifolds
Misha Verbitsky (ITEP, Moscow)
Lefschetz SL(2)-action and cohomology of Kaehler manifolds
[ Abstract ]
Let M be compact Kaehler manifold. It is well
known that any Kaehler form generates a Lefschetz SL(2)-triple
acting on cohomology of M. This action can be used to compute
cohomology of M. If M is a hyperkaehler manifold, of real
dimension 4n, then the subalgebra of its cohomology generated by
the second cohomology is isomorphic to a polynomial algebra,
up to the middle degree.
Let M be compact Kaehler manifold. It is well
known that any Kaehler form generates a Lefschetz SL(2)-triple
acting on cohomology of M. This action can be used to compute
cohomology of M. If M is a hyperkaehler manifold, of real
dimension 4n, then the subalgebra of its cohomology generated by
the second cohomology is isomorphic to a polynomial algebra,
up to the middle degree.
2008/11/01
Monthly Seminar on Arithmetic of Automorphic Forms
13:30-16:00 Room #123 (Graduate School of Math. Sci. Bldg.)
宗野恵樹 (東京大学数理科学) 13:30-14:30
$(\\mathfrka{g},K)$-module structure of the principal series of $GL(3,\\mathfrak{C})$
Toward effectively computable integral basis of simple $\\mathbfrak{gl}_4$-modules of finite dimension. (II)
宗野恵樹 (東京大学数理科学) 13:30-14:30
$(\\mathfrka{g},K)$-module structure of the principal series of $GL(3,\\mathfrak{C})$
[ Abstract ]
We give explicit description of the action of $\\mathfrak{gl}(3,\\mathbf{C}$ to the whole space of $K$-finite vectors of a given principal series representation of $GL(3,\\mathbf{C})$.
織田孝幸 (東京大学数理科学) 15:00-16:00We give explicit description of the action of $\\mathfrak{gl}(3,\\mathbf{C}$ to the whole space of $K$-finite vectors of a given principal series representation of $GL(3,\\mathbf{C})$.
Toward effectively computable integral basis of simple $\\mathbfrak{gl}_4$-modules of finite dimension. (II)
[ Abstract ]
This is a continuation of the talk at Osaka in the occation of Kanrei workshop of Prof. T. Ibukiyama.
We discuss a part of the injection $V_{\\lambda} \\rightarrow \\mathfrak{p} \\otimes V_{\\lambda}$. Here $V_{\\lambda}$ is a simple module with highest weight $\\lambda$, and $\\mathfrak{p}$ is the adjoint representation with highest weight $(1,0,0,-1)$.
This is a continuation of the talk at Osaka in the occation of Kanrei workshop of Prof. T. Ibukiyama.
We discuss a part of the injection $V_{\\lambda} \\rightarrow \\mathfrak{p} \\otimes V_{\\lambda}$. Here $V_{\\lambda}$ is a simple module with highest weight $\\lambda$, and $\\mathfrak{p}$ is the adjoint representation with highest weight $(1,0,0,-1)$.
2008/10/31
Lecture Series on Mathematical Sciences in Soceity
16:20-17:50 Room #128 (Graduate School of Math. Sci. Bldg.)
岡本 龍明 (NTT研究所)
暗号の実践編
岡本 龍明 (NTT研究所)
暗号の実践編
2008/10/30
Seminar on Probability and Statistics
16:20-17:30 Room #270 (Graduate School of Math. Sci. Bldg.)
若木 宏文 (広島大学大学院理学研究科)
正規母集団に関する検定統計量の分布の漸近展開の誤差評価
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2008/08.html
若木 宏文 (広島大学大学院理学研究科)
正規母集団に関する検定統計量の分布の漸近展開の誤差評価
[ Abstract ]
多変量正規母集団に関する検定統計量の帰無分布の特性関数は、いくつかの多変量ガ ンマ関数の比として表されることが多い。Box (1949) はガンマ関数の漸近展開(ス ターリングの公式)を用いて、このような分布の大標本漸近展開公式を導出したが、 導出過程での剰余項を詳しく評価してゆくことで、分布関数の漸近展開近似の計算可 能な誤差限界を導出することができる。いくつかの検定統計量に対する大標本漸近展 開近似の誤差限界を導出し、高次元・大標本の枠組みで得られているエッジワース展 開近似の誤差限界と比較する。
[ Reference URL ]多変量正規母集団に関する検定統計量の帰無分布の特性関数は、いくつかの多変量ガ ンマ関数の比として表されることが多い。Box (1949) はガンマ関数の漸近展開(ス ターリングの公式)を用いて、このような分布の大標本漸近展開公式を導出したが、 導出過程での剰余項を詳しく評価してゆくことで、分布関数の漸近展開近似の計算可 能な誤差限界を導出することができる。いくつかの検定統計量に対する大標本漸近展 開近似の誤差限界を導出し、高次元・大標本の枠組みで得られているエッジワース展 開近似の誤差限界と比較する。
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2008/08.html
Lectures
10:00-11:00 Room #002 (Graduate School of Math. Sci. Bldg.)
Arnaud DUCROT (University of Bordeaux)
Travelling wave solutions for an infection age structured epidemic model
Arnaud DUCROT (University of Bordeaux)
Travelling wave solutions for an infection age structured epidemic model
[ Abstract ]
In this lecture, we study the existence of travelling wave solutions for a class of epidemic model structured in space and with respect ot the age of infection. We obtain necessary and sufficient conditions for the existence of travelling waves for such a class of problems. As a consequence, we also derive the existence of travelling waves for a class of functional partial differential equations.
In this lecture, we study the existence of travelling wave solutions for a class of epidemic model structured in space and with respect ot the age of infection. We obtain necessary and sufficient conditions for the existence of travelling waves for such a class of problems. As a consequence, we also derive the existence of travelling waves for a class of functional partial differential equations.
2008/10/29
Seminar on Mathematics for various disciplines
10:30-11:30 Room #056 (Graduate School of Math. Sci. Bldg.)
木村芳文 (名古屋大学(多元数理科学研究科))
Stratified turbulence as an element of geophysical fluid dynamics
木村芳文 (名古屋大学(多元数理科学研究科))
Stratified turbulence as an element of geophysical fluid dynamics
[ Abstract ]
Density stratification and rotation are the two major mechanisms that characterize the whole geophysical flows. In this talk, focusing on stable stratification, I will introduce some statistical, mechanical and geometrical aspects of stratified turbulence by showing the recent results of large scale computer simulations.
Density stratification and rotation are the two major mechanisms that characterize the whole geophysical flows. In this talk, focusing on stable stratification, I will introduce some statistical, mechanical and geometrical aspects of stratified turbulence by showing the recent results of large scale computer simulations.
Number Theory Seminar
16:30-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Daniel Caro (Université de Caen)
Overholonomicity of overconvergence $F$-isocrystals on smooth varieties
Daniel Caro (Université de Caen)
Overholonomicity of overconvergence $F$-isocrystals on smooth varieties
[ Abstract ]
Let $¥mathcal{V}$ be a complete discrete valuation ring
of characteristic $0$, with perfect residue field $k$ of
characteristic $p>0$. In order to construct $p$-adic coefficients
over $k$-varieties, Berthelot introduced the theory of
overconvergent $F$-isocrystals, i.e overconvergent isocrystals with
Frobenius structure. Moreover, to get a $p$-adic cohomology over
$k$-varieties stable under cohomological operations, Berthelot built
the theory of arithmetic $F$-$¥mathcal{D}$-modules. In this talk,
after recalling some elements of these theories, we introduce the
notion of overholonomicity with is a property as stable as the
holonomicity in the classical theory of $¥mathcal{D}$-modules. The
goal of the talk is to prove the overholonomicity of arithmetic
$¥mathcal{D}$-modules associated to overconvergent $F$-isocrystals
over smooth $k$-varieties. In the proof we need Christol's transfert
theorem, a comparison theorem between relative log rigid cohomology
and relative rigid cohomology and last but not least Kedlaya's
semistable reduction theorem. This is a joint work with Nobuo
Tsuzuki.
Let $¥mathcal{V}$ be a complete discrete valuation ring
of characteristic $0$, with perfect residue field $k$ of
characteristic $p>0$. In order to construct $p$-adic coefficients
over $k$-varieties, Berthelot introduced the theory of
overconvergent $F$-isocrystals, i.e overconvergent isocrystals with
Frobenius structure. Moreover, to get a $p$-adic cohomology over
$k$-varieties stable under cohomological operations, Berthelot built
the theory of arithmetic $F$-$¥mathcal{D}$-modules. In this talk,
after recalling some elements of these theories, we introduce the
notion of overholonomicity with is a property as stable as the
holonomicity in the classical theory of $¥mathcal{D}$-modules. The
goal of the talk is to prove the overholonomicity of arithmetic
$¥mathcal{D}$-modules associated to overconvergent $F$-isocrystals
over smooth $k$-varieties. In the proof we need Christol's transfert
theorem, a comparison theorem between relative log rigid cohomology
and relative rigid cohomology and last but not least Kedlaya's
semistable reduction theorem. This is a joint work with Nobuo
Tsuzuki.
Seminar on Probability and Statistics
16:20-17:30 Room #128 (Graduate School of Math. Sci. Bldg.)
下平 英寿 (東京工業大学 情報理工学研究科)
マルチスケール・ブートストラップ法による確率値計算とFDR
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2008/07.html
下平 英寿 (東京工業大学 情報理工学研究科)
マルチスケール・ブートストラップ法による確率値計算とFDR
[ Abstract ]
ブートストラップ確率はブートストラップ標本において仮説が支持される頻度であり, その実装の容易さから広く用いられている.たとえば,階層型クラスタリングにおいて得られたクラスタ が真実かどうかを判断する指標になる.ところが頻度論の不偏検定の立場で見ると,ブートストラップ確率 には無視できないくらい十分に大きいバイアスがあり,それはある種のパラメータ空間において仮説を あらわす領域の境界の曲率として解釈できることが知られている.本講演ではリサンプリングにおける データサイズを変化させたときの「スケール変換則」からバイアス補正する手法を紹介する. 曲面のテイラー展開のかわりにフーリエ変換をつかった漸近理論であり,錐のように必ずしもなめらかな曲面 でない場合でも適用できる (Shimodaira 2008).また,スケール変換則のアイデアをベイズ的なFalse Discovery Rateの計算に応用した最近の結果についても簡単に触れる.
[ Reference URL ]ブートストラップ確率はブートストラップ標本において仮説が支持される頻度であり, その実装の容易さから広く用いられている.たとえば,階層型クラスタリングにおいて得られたクラスタ が真実かどうかを判断する指標になる.ところが頻度論の不偏検定の立場で見ると,ブートストラップ確率 には無視できないくらい十分に大きいバイアスがあり,それはある種のパラメータ空間において仮説を あらわす領域の境界の曲率として解釈できることが知られている.本講演ではリサンプリングにおける データサイズを変化させたときの「スケール変換則」からバイアス補正する手法を紹介する. 曲面のテイラー展開のかわりにフーリエ変換をつかった漸近理論であり,錐のように必ずしもなめらかな曲面 でない場合でも適用できる (Shimodaira 2008).また,スケール変換則のアイデアをベイズ的なFalse Discovery Rateの計算に応用した最近の結果についても簡単に触れる.
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2008/07.html
2008/10/28
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
清野 和彦 (東京大学大学院数理科学研究科)
Nonsmoothable group actions on spin 4-manifolds
清野 和彦 (東京大学大学院数理科学研究科)
Nonsmoothable group actions on spin 4-manifolds
[ Abstract ]
We call a locally linear group action on a topological manifold nonsmoothable
if the action is not smooth with respect to any possible smooth structure.
We show in this lecture that every closed, simply connected, spin topological 4-manifold
not homeomorphic to neither S^2\\times S^2 nor S^4 allows a nonsmoothable
group action of any cyclic group with sufficiently large prime order
which depends on the manifold.
We call a locally linear group action on a topological manifold nonsmoothable
if the action is not smooth with respect to any possible smooth structure.
We show in this lecture that every closed, simply connected, spin topological 4-manifold
not homeomorphic to neither S^2\\times S^2 nor S^4 allows a nonsmoothable
group action of any cyclic group with sufficiently large prime order
which depends on the manifold.
Lie Groups and Representation Theory
16:30-18:00 Room #126 (Graduate School of Math. Sci. Bldg.)
Joachim Hilgert (Paderborn University)
Chevalley's restriction theorem for supersymmetric Riemannian symmetric spaces
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html
Joachim Hilgert (Paderborn University)
Chevalley's restriction theorem for supersymmetric Riemannian symmetric spaces
[ Abstract ]
We start by explaining the concept of a supersymmetric Riemannian symmetric spaces and present the examples studied by Zirnbauer in the context of universality classes of random matrices. For these classes we then show how to formulate and prove an analog of Chevalley's restriction theorem for invariant super-functions.
This is joint work with A. Alldridge (Paderborn) and M. Zirnbauer (Cologne)
[ Reference URL ]We start by explaining the concept of a supersymmetric Riemannian symmetric spaces and present the examples studied by Zirnbauer in the context of universality classes of random matrices. For these classes we then show how to formulate and prove an analog of Chevalley's restriction theorem for invariant super-functions.
This is joint work with A. Alldridge (Paderborn) and M. Zirnbauer (Cologne)
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html
< Previous 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195 Next >
