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Seminar information archive
Seminar information archive ～04/24｜Today's seminar 04/25 | Future seminars 04/26～
2009/10/30
Lecture Series on Mathematical Sciences in Soceity
16:20-17:50 Room #117 (Graduate School of Math. Sci. Bldg.)
辻 芳彦 ((社)日本アクチュアリー会事務局事務局長)
アクチュアリーの役割Ⅱ
辻 芳彦 ((社)日本アクチュアリー会事務局事務局長)
アクチュアリーの役割Ⅱ
GCOE Seminars
15:00-16:00 Room #370 (Graduate School of Math. Sci. Bldg.)
Shuai Lu (Johann Radon Institute)
Regularized total least squares: computational aspects and error bounds
Shuai Lu (Johann Radon Institute)
Regularized total least squares: computational aspects and error bounds
[ Abstract ]
For solving linear ill-posed problems, regularization methods are required when the right hand side and/or the operator are corrupted by some noise. In the present talk, regularized solutions are constructed using regularized total least squares and dual regularized total least squares. We discuss computational aspects and provide order optimal error bounds that characterize the accuracy of the regularized solutions. The results extend earlier results where the operator is exactly given. We also present some numerical experiments, which shed light on the relationship between RTLS, dual RTLS and the standard Tikhonov regularization.
For solving linear ill-posed problems, regularization methods are required when the right hand side and/or the operator are corrupted by some noise. In the present talk, regularized solutions are constructed using regularized total least squares and dual regularized total least squares. We discuss computational aspects and provide order optimal error bounds that characterize the accuracy of the regularized solutions. The results extend earlier results where the operator is exactly given. We also present some numerical experiments, which shed light on the relationship between RTLS, dual RTLS and the standard Tikhonov regularization.
2009/10/29
Operator Algebra Seminars
16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Robert Coquereaux (CNRS/CPT, Marseille)
Fusion graphs for Lie groups at level k and quantum symmetries
Robert Coquereaux (CNRS/CPT, Marseille)
Fusion graphs for Lie groups at level k and quantum symmetries
Lectures
16:30-17:30 Room #270 (Graduate School of Math. Sci. Bldg.)
Michael I. Tribelsky (MIREA (Technical University), Moscow, Russia)
Spectral properties of Nikolaevskiy chaos
Michael I. Tribelsky (MIREA (Technical University), Moscow, Russia)
Spectral properties of Nikolaevskiy chaos
2009/10/28
Lectures
16:30-17:30 Room #370 (Graduate School of Math. Sci. Bldg.)
Michael Ruzhansky (Imperial College, London)
Dispersive and Strichartz estimates for hyperbolic equations of general form
Michael Ruzhansky (Imperial College, London)
Dispersive and Strichartz estimates for hyperbolic equations of general form
2009/10/27
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
Alex Bene (IPMU)
A new appearance of the Morita-Penner cocycle
Alex Bene (IPMU)
A new appearance of the Morita-Penner cocycle
[ Abstract ]
In this talk, I will recall the Morita-Penner cocycle on the dual fatgraph complex for a surface with one boundary component. This cocycle, when restricted to paths representing elements of the mapping class group, represents the extended first Johnson homomorphism \\tau_1, thus can be viewed as a (in some specific sense canonical) "groupoid extension" of \\tau_1. There are now several different contexts in which this cocycle can be constructed, and in this talk I will briefly review several of them, including one discovered in the context of finite type invariants of homology cylinders in joint work with J.E. Andersen, J-B. Meilhan, and R.C. Penner.
In this talk, I will recall the Morita-Penner cocycle on the dual fatgraph complex for a surface with one boundary component. This cocycle, when restricted to paths representing elements of the mapping class group, represents the extended first Johnson homomorphism \\tau_1, thus can be viewed as a (in some specific sense canonical) "groupoid extension" of \\tau_1. There are now several different contexts in which this cocycle can be constructed, and in this talk I will briefly review several of them, including one discovered in the context of finite type invariants of homology cylinders in joint work with J.E. Andersen, J-B. Meilhan, and R.C. Penner.
2009/10/26
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Pietro Corvaja (Università di Udine)
On Vojta's conjecture in the split function field case
Pietro Corvaja (Università di Udine)
On Vojta's conjecture in the split function field case
2009/10/23
Lecture Series on Mathematical Sciences in Soceity
16:20-17:50 Room #117 (Graduate School of Math. Sci. Bldg.)
辻 芳彦 ((社)日本アクチュアリー会事務局事務局長)
アクチュアリーの役割Ⅰ
辻 芳彦 ((社)日本アクチュアリー会事務局事務局長)
アクチュアリーの役割Ⅰ
Colloquium
16:30-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)
辻 雄 (東京大学大学院数理科学研究科)
p進エタール層のp進Hodge理論
辻 雄 (東京大学大学院数理科学研究科)
p進エタール層のp進Hodge理論
[ Abstract ]
複素や実の多様体の特異コホモロジーを微分形式の言葉で記述する理論として、de Rhamの定理やHodge理論が良く知られている。p進Hodge理論は、これらの類似をp進体上の代数多様体のp進エタール・コホモロジーで考える理論である。p進エタール・コホモロジーにはp進体の絶対ガロア群が非常に複雑に作用しており、この作用を分かりやすい別の言葉で記述する理論の構築が、p進Hodge理論における大きな課題となっている。前半でp進Hodge理論の研究の歴史や背景について概観した後、後半ではp進体の絶対ガロア群のp進表現の相対版である、p進体上定義された代数多様体上のp進エタール層についての最近の研究を紹介する。
複素や実の多様体の特異コホモロジーを微分形式の言葉で記述する理論として、de Rhamの定理やHodge理論が良く知られている。p進Hodge理論は、これらの類似をp進体上の代数多様体のp進エタール・コホモロジーで考える理論である。p進エタール・コホモロジーにはp進体の絶対ガロア群が非常に複雑に作用しており、この作用を分かりやすい別の言葉で記述する理論の構築が、p進Hodge理論における大きな課題となっている。前半でp進Hodge理論の研究の歴史や背景について概観した後、後半ではp進体の絶対ガロア群のp進表現の相対版である、p進体上定義された代数多様体上のp進エタール層についての最近の研究を紹介する。
Seminar on Probability and Statistics
15:00-16:10 Room #128 (Graduate School of Math. Sci. Bldg.)
Vladimir Bogachev (Moscow State University)
On invariant measures of diffusion processes with unbounded drifts
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/08.html
Vladimir Bogachev (Moscow State University)
On invariant measures of diffusion processes with unbounded drifts
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/08.html
2009/10/22
Operator Algebra Seminars
16:30-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Adam Skalski (Lancaster University)
On some questions related to Voiculescu's noncommutative topological entropy
Adam Skalski (Lancaster University)
On some questions related to Voiculescu's noncommutative topological entropy
Lectures
10:40-12:10 Room #128 (Graduate School of Math. Sci. Bldg.)
竹崎正道 (UCLA)
冨田竹崎理論とその応用 (3)
竹崎正道 (UCLA)
冨田竹崎理論とその応用 (3)
Seminar on Probability and Statistics
16:30-17:40 Room #122 (Graduate School of Math. Sci. Bldg.)
深澤 正彰 (大阪大学 金融・保険教育研究センター)
ASYMPTOTICALLY EFFICIENT DISCRETE HEDGING
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/07.html
深澤 正彰 (大阪大学 金融・保険教育研究センター)
ASYMPTOTICALLY EFFICIENT DISCRETE HEDGING
[ Abstract ]
The notion of asymptotic efficiency for discrete hedging is introduced and a discretizing strategy which is asymptotically efficient is given explicitly. A lower bound for asymptotic risk of discrete hedging is given, which is attained by a simple discretization scheme. Numerical results for delta hedging in the Black-Scholes model are also presented.
[ Reference URL ]The notion of asymptotic efficiency for discrete hedging is introduced and a discretizing strategy which is asymptotically efficient is given explicitly. A lower bound for asymptotic risk of discrete hedging is given, which is attained by a simple discretization scheme. Numerical results for delta hedging in the Black-Scholes model are also presented.
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/07.html
thesis presentations
13:00-14:15 Room #122 (Graduate School of Math. Sci. Bldg.)
深澤 正彰 (大阪大学 金融・保険教育研究センター)
Asymptotic Analysis for Stochastic Volatility (確率的ボラティティの漸近解析)
深澤 正彰 (大阪大学 金融・保険教育研究センター)
Asymptotic Analysis for Stochastic Volatility (確率的ボラティティの漸近解析)
2009/10/21
GCOE lecture series
15:30-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)
Jean-Dominique Deuschel (TU Berlin)
Mini course on the gradient models, Ⅲ: Non convex potentials at high temperature
Jean-Dominique Deuschel (TU Berlin)
Mini course on the gradient models, Ⅲ: Non convex potentials at high temperature
[ Abstract ]
In the non convex case, the situation is much more complicated. In fact Biskup and Kotecky describe a non convex model with several ergodic components. We investigate a model with non convex interaction for which unicity of the ergodic component, scaling limits and large deviations can be proved at sufficiently high temperature. We show how integration can generate strictly convex potential, more precisely that marginal measure of the even sites satisfies the random walk representation. This is a joint work with Codina Cotar and Nicolas Petrelis.
In the non convex case, the situation is much more complicated. In fact Biskup and Kotecky describe a non convex model with several ergodic components. We investigate a model with non convex interaction for which unicity of the ergodic component, scaling limits and large deviations can be proved at sufficiently high temperature. We show how integration can generate strictly convex potential, more precisely that marginal measure of the even sites satisfies the random walk representation. This is a joint work with Codina Cotar and Nicolas Petrelis.
Number Theory Seminar
16:30-17:30 Room #056 (Graduate School of Math. Sci. Bldg.)
Bernard Le Stum (Université de Rennes 1)
The local Simpson correspondence in positive characteristic
Bernard Le Stum (Université de Rennes 1)
The local Simpson correspondence in positive characteristic
[ Abstract ]
A Simpson correspondance should relate Higgs bundles to differential modules (or local systems). We stick here to positive characteristic and recall some old and recent results : Cartier isomorphism, Van der Put's classification, Kaneda's theorem and Ogus-Vologodsky local theory. We'll try to explain how the notion of Azumaya algebra is a convenient tool to unify these results. Our main theorem is the equivalence between quasi-nilpotent differential modules of level m and quasi-nilpotent Higgs Bundles (depending on a lifting of Frobenius mod p-squared). This result is a direct generalization of the previous ones. The main point is to understand the Azumaya nature of the ring of differential operators of level m. Following Berthelot, we actually use the dual theory and study the partial divided power neighborhood of the diagonal.
A Simpson correspondance should relate Higgs bundles to differential modules (or local systems). We stick here to positive characteristic and recall some old and recent results : Cartier isomorphism, Van der Put's classification, Kaneda's theorem and Ogus-Vologodsky local theory. We'll try to explain how the notion of Azumaya algebra is a convenient tool to unify these results. Our main theorem is the equivalence between quasi-nilpotent differential modules of level m and quasi-nilpotent Higgs Bundles (depending on a lifting of Frobenius mod p-squared). This result is a direct generalization of the previous ones. The main point is to understand the Azumaya nature of the ring of differential operators of level m. Following Berthelot, we actually use the dual theory and study the partial divided power neighborhood of the diagonal.
Lectures
14:40-16:10 Room #128 (Graduate School of Math. Sci. Bldg.)
竹崎正道 (UCLA)
冨田竹崎理論とその応用 (2)
竹崎正道 (UCLA)
冨田竹崎理論とその応用 (2)
Seminar on Probability and Statistics
15:00-16:10 Room #002 (Graduate School of Math. Sci. Bldg.)
田中 冬彦 (科学技術振興機構さきがけ)
AR過程の優調和事前分布と偏自己相関係数による表示
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/06.html
田中 冬彦 (科学技術振興機構さきがけ)
AR過程の優調和事前分布と偏自己相関係数による表示
[ Abstract ]
Tanaka and Komaki(2008)では時系列データが2次の自己回帰過程(AR過程)に従う 時のスペクトル密度の推定を考え、優調和事前分布に基づいたベイズスペクトル 密度の方がジェフリーズ事前分布に基づいたベイズスペクトル密度よりも精度よ く推定できることを示している。高次のAR過程での優調和事前分布はTanaka( 2009)によって初めて与えられたが、特性方程式の根を用いた表示のため、数値 実験を行う上では取り扱いづらかった。本発表では高次のAR過程への応用を念頭 において偏自己相関係数(PAC)によるパラメータ表示を導入し数値実験した結 果を紹介する。 また、PACパラメータによる表示は解析的な取扱いをする上でも利点があり、AR 過程の優調和事前分布に関して新しく得られた結果も幾つか紹介したい。
[ Reference URL ]Tanaka and Komaki(2008)では時系列データが2次の自己回帰過程(AR過程)に従う 時のスペクトル密度の推定を考え、優調和事前分布に基づいたベイズスペクトル 密度の方がジェフリーズ事前分布に基づいたベイズスペクトル密度よりも精度よ く推定できることを示している。高次のAR過程での優調和事前分布はTanaka( 2009)によって初めて与えられたが、特性方程式の根を用いた表示のため、数値 実験を行う上では取り扱いづらかった。本発表では高次のAR過程への応用を念頭 において偏自己相関係数(PAC)によるパラメータ表示を導入し数値実験した結 果を紹介する。 また、PACパラメータによる表示は解析的な取扱いをする上でも利点があり、AR 過程の優調和事前分布に関して新しく得られた結果も幾つか紹介したい。
https://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2009/06.html
2009/10/20
Tuesday Seminar on Topology
16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)
吉田 尚彦 (明治大学大学院理工学研究科)
Torus fibrations and localization of index
吉田 尚彦 (明治大学大学院理工学研究科)
Torus fibrations and localization of index
[ Abstract ]
I will describe a localization of index of a Dirac type operator.
We make use of a structure of torus fibration, but the mechanism
of the localization does not rely on any group action. In the case of
Lagrangian fibration, we show that the index is described as a sum of
the contributions from Bohr-Sommerfeld fibers and singular fibers.
To show the localization we introduce a deformation of a Dirac type
operator for a manifold equipped with a fiber bundle structure which
satisfies a kind of acyclic condition. The deformation allows an
interpretation as an adiabatic limit or an infinite dimensional analogue
of Witten deformation.
Joint work with Hajime Fujita and Mikio Furuta.
I will describe a localization of index of a Dirac type operator.
We make use of a structure of torus fibration, but the mechanism
of the localization does not rely on any group action. In the case of
Lagrangian fibration, we show that the index is described as a sum of
the contributions from Bohr-Sommerfeld fibers and singular fibers.
To show the localization we introduce a deformation of a Dirac type
operator for a manifold equipped with a fiber bundle structure which
satisfies a kind of acyclic condition. The deformation allows an
interpretation as an adiabatic limit or an infinite dimensional analogue
of Witten deformation.
Joint work with Hajime Fujita and Mikio Furuta.
Lectures
14:40-16:10 Room #128 (Graduate School of Math. Sci. Bldg.)
竹崎正道 (UCLA)
冨田竹崎理論とその応用 (1)
竹崎正道 (UCLA)
冨田竹崎理論とその応用 (1)
2009/10/19
Seminar on Geometric Complex Analysis
10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)
濱野佐知子 (松江高専)
Variation formulas for principal functions (II)
濱野佐知子 (松江高専)
Variation formulas for principal functions (II)
Algebraic Geometry Seminar
16:40-18:10 Room #126 (Graduate School of Math. Sci. Bldg.)
渡辺 究 (早稲田大学基幹理工学研究科)
ファノ多様体上の有理曲線の鎖の長さについて
渡辺 究 (早稲田大学基幹理工学研究科)
ファノ多様体上の有理曲線の鎖の長さについて
[ Abstract ]
ピカール数1のファノ多様体に対し、一般の二点を結ぶために必要な
極小有理曲線の本数を「長さ」と呼び、それについて考える。特に、5次元以下の
ファノ多様体や余指数が3以下のファノ多様体などに対し、長さを求める。
ピカール数1のファノ多様体に対し、一般の二点を結ぶために必要な
極小有理曲線の本数を「長さ」と呼び、それについて考える。特に、5次元以下の
ファノ多様体や余指数が3以下のファノ多様体などに対し、長さを求める。
2009/10/15
Lecture Series on Mathematical Sciences in Soceity
16:20-17:50 Room #056 (Graduate School of Math. Sci. Bldg.)
藤原 洋 (インターネット総合研究所代表取締役所長)
社会における学位取得者の役割Ⅰ
藤原 洋 (インターネット総合研究所代表取締役所長)
社会における学位取得者の役割Ⅰ
Lie Groups and Representation Theory
16:30-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)
土岡俊介 (RIMS, Kyoto University)
Hecke-Clifford superalgebras and crystals of type $D^{(2)}_{l}$
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html
土岡俊介 (RIMS, Kyoto University)
Hecke-Clifford superalgebras and crystals of type $D^{(2)}_{l}$
[ Abstract ]
It is known that we can sometimes describe the representation theory of ``Hecke algebra'' by ``Lie theory''. Famous examples that involve the Lie theory of type $A^{(1)}_n$ are Lascoux-Leclerc-Thibon's interpretation of Kleshchev's modular branching rule for the symmetric groups and Ariki's theorem generalizing Lascoux-Leclerc-Thibon's conjecture for the Iwahori-Hecke algebras of type A.
Brundan and Kleshchev showed that some parts of the representation theory of the affine Hecke-Clifford superalgebras and its finite-dimensional ``cyclotomic'' quotients are controlled by the Lie theory of type $A^{(2)}_{2l}$ when the quantum parameter $q$ is a primitive $(2l+1)$-th root of unity.
In this talk, we show that similar theorems hold when $q$ is a primitive $4l$-th root of unity by replacing the Lie theory of type $A^{(2)}_{2l}$ with that of type $D^{(2)}_{l}$.
[ Reference URL ]It is known that we can sometimes describe the representation theory of ``Hecke algebra'' by ``Lie theory''. Famous examples that involve the Lie theory of type $A^{(1)}_n$ are Lascoux-Leclerc-Thibon's interpretation of Kleshchev's modular branching rule for the symmetric groups and Ariki's theorem generalizing Lascoux-Leclerc-Thibon's conjecture for the Iwahori-Hecke algebras of type A.
Brundan and Kleshchev showed that some parts of the representation theory of the affine Hecke-Clifford superalgebras and its finite-dimensional ``cyclotomic'' quotients are controlled by the Lie theory of type $A^{(2)}_{2l}$ when the quantum parameter $q$ is a primitive $(2l+1)$-th root of unity.
In this talk, we show that similar theorems hold when $q$ is a primitive $4l$-th root of unity by replacing the Lie theory of type $A^{(2)}_{2l}$ with that of type $D^{(2)}_{l}$.
https://www.ms.u-tokyo.ac.jp/~toshi/seminar/ut-seminar.html
2009/10/14
GCOE lecture series
15:30-17:00 Room #128 (Graduate School of Math. Sci. Bldg.)
Claudio Landim (IMPA, Brazil)
Macroscopic fluctuation theory for nonequilibrium stationary states, Ⅳ
Claudio Landim (IMPA, Brazil)
Macroscopic fluctuation theory for nonequilibrium stationary states, Ⅳ
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