過去の記録 ~01/25本日 01/26 | 今後の予定 01/27~



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
二木 昭人 氏 (東京大学大学院数理科学研究科)
Geometric flows and their self-similar solutions
[ 講演概要 ]
In the first half of this expository talk we consider the Ricci flow and its self-similar solutions,
namely the Ricci solitons. We then specialize in the K\\"ahler case and discuss on the K\\"ahler-Einstein
problem. In the second half of this talk we consider the mean curvature flow and its self-similar
solutions, and see common aspects of the two geometric flows.



13:30-15:00   数理科学研究科棟(駒場) 122号室
Robert Laterveer 氏 (CNRS, IRMA, Université de Strasbourg)
Weak Lefschetz for divisors (ENGLISH)
[ 講演概要 ]
Let $X$ be a complex projective variety (possibly singular), and $Y\\subset X$ a generic hyperplane section. We prove several weak Lefschetz results concerning the restriction $A^1(X)_{\\qq}\\to A^1(Y)_{\\qq}$, where $A^1$ denotes Fulton--MacPherson's operational Chow cohomology group. In addition, we reprove (and slightly extend) a weak Lefschetz result concerning the Chow group of Weil divisors first proven by Ravindra and Srinivas. As an application of these weak Lefschetz results, we can say something about when the natural map from the Picard group to $A^1$ is an isomorphism.


15:30-17:00   数理科学研究科棟(駒場) 122号室
大川 領 氏 (京都大学数理解析研究所)
Frobenius morphisms and derived categories on two dimensional toric Deligne--Mumford stacks (JAPANESE)
[ 講演概要 ]
For a toric Deligne-Mumford (DM) stack over the complex number field, we can consider a certain generalization of the Frobenius endomorphism. For such an endomorphism of a two-dimensional toric DM stack, we show that the push-forward of the structure sheaf generates the bounded derived category of coherent sheaves on the stack. This is joint work with Hokuto Uehara.



16:00-17:30   数理科学研究科棟(駒場) 128号室
Bernold Fiedler 氏 (Free University of Berlin)
Fusco-Rocha meanders: from Temperley-Lieb algebras to black holes
[ 講演概要 ]
Fusco and Rocha studied Neumann boundary value problems for ODEs of second order via a shooting approach. They introduced the notion of what we now call Sturm permutation. These permutation relate, on the one hand, to a special class of meandering curves as introduced by Arnol'd in a singularity context. On the other hand, their special class became central in the study of global attractors of parabolic PDEs of Sturm type.

We discuss relations of Fusco-Rocha meanders with further areas: the multiplicative and trace structure in Temperley-Lieb algebras, discrete versions of Cartesian billiards, and the problem of constructing initial conditions for black hole dynamics which satisfy the Einstein constraints. We also risk a brief glimpse at the long and meandric history of meander patterns themselves.

This is joint work with Juliette Hell, Brian Smith, Carlos Rocha, Pablo Castaneda, and Matthias Wolfrum.



13:30-16:00   数理科学研究科棟(駒場) 123号室
宮崎 直 氏 (北里大学) 13:30-14:30
SU(2,1)とSU(3,1)の大きい離散系列表現の行列係数 (JAPANESE)
[ 講演概要 ]
成田宏秋 氏 (熊本大学) 15:00-16:00
GSp(1,1)のRankin型のL関数の中心値の正値性と超幾何級数の特殊値 (JAPANESE)
[ 講演概要 ]
We discuss the strict positivity of the central values of
certain convolution type L-functions for several theta lifts to GSp(1,1). Such strict positivity is closely related to special values of some hypergeometric functions.



17:00-18:00   数理科学研究科棟(駒場) 002号室
Tea: 16:30 - 17:00 コモンルーム
Piotr Nowak 氏 (the Institute of Mathematics, Polish Academy of Sciences)
Poincare inequalities, rigid groups and applications (ENGLISH)
[ 講演概要 ]
Kazhdan’s property (T) for a group G can be expressed as a
fixed point property for affine isometric actions of G on a Hilbert
space. This definition generalizes naturally to other normed spaces. In
this talk we will focus on the spectral (aka geometric) method for
proving property (T), based on the work of Garland and studied earlier
by Pansu, Zuk, Ballmann-Swiatkowski, Dymara-Januszkiewicz
(“lambda_1>1/2” conditions) and we generalize it to to the setting of
all reflexive Banach spaces.
As applications we will show estimates of the conformal dimension of the
boundary of random hyperbolic groups in the Gromov density model and
present progress on Shalom’s conjecture on vanishing of 1-cohomology
with coefficients in uniformly bounded representations on Hilbert spaces.



10:30-11:45   数理科学研究科棟(駒場) 123号室
松村 慎一 氏 (大学院数理科学研究科)
Studies on the asymptotic invariants of cohomology groups and the positivity in complex geometry (コホモロジー群の漸近的な不変量と複素幾何学における正値性の研究) (JAPANESE)



11:00-12:15   数理科学研究科棟(駒場) 128号室
三村 与士文 氏 (東京大学大学院数理科学研究科)
The variational formulation of the fully parabolic Keller-Segel system with degenerate diffusion (退化拡散項を持つ完全放物型Keller-Segel系に対する変分的定式化) (JAPANESE)



15:30-17:00   数理科学研究科棟(駒場) 122号室
Gianluca Pacienza 氏 (Université de Strasbourg)
Log Bend-and-Break on Deligne-Mumford stacks (ENGLISH)
[ 講演概要 ]
We prove a logarithmic Bend-and-Break lemma on a LCI Deligne-Mumford stacks with projective moduli space and integral boundary divisor. As a by-product we obtain a logarithmic version of the Miyaoka-Mori numerical criterion of uniruledness for DM stacks (under additional conditions on the boundary and on the non-schematic locus) and a Cone Theorem for Deligne-Mumford stacks with boundary. These results hold on an algebraically closed field of any characteristic. This is joint work with Michael McQuillan.



14:00-17:00   数理科学研究科棟(駒場) 006号室
参加をご希望される方は鎌谷 (阪大基礎工); kamatani at sigmath.es.osaka-u.ac.jpまでご連絡ください.
植野 剛 氏 (科学技術振興機構 湊離散構造処理系プロジェクト)
強化学習を統計推論の観点から考える (JAPANESE)
[ 講演概要 ]
強化学習は心理学, 神経科学, コンピュータ科学, 制御工学など複数の研究分野に起因する機械学習法の1つである. 強化学習は, 未知の環境に置かれた学習対象(エージェント)が試行錯誤を通じて得た自身の成功・失敗体験(報酬)から行動方策を自律的に学習するエージェント学習の一手法である. 強化学習の特徴は, 他のエージェント学習法と異なり, 環境のダイナミクスを推定することなく, 得られた報酬から行動方策を直接学習することが可能な点である. したがって, 環境のダイナミクスのモデル化が必要なく, 環境が強い非線形ダイナミクスを持つ場合でも方策学習が原理的に可能である. よって, この望ましい性質により,様々な実問題に応用され, 多大な成功を収めている.

一方, 強化学習の理論面に目を向けると, これまで提案されている強化学習法の性能評価は, 計算機実験など経験的に行われており, 理論的, 特に統計的な評価はほとんど行われていない. この要因の1つとして, 強化学習が最適制御を基礎に数理が展開されており, これまで強化学習の統計的な解釈がなされていないことが考えられる. したがって, 本研究では, 強化学習の統計的観点から見直し, より一般的な統計推論問題として再定式化することを目指す. そして統計学習分野で培われてきた解析手法を応用し, これまで明らかにされてこなかった強化学習の理論的な性質を解明する(そうなるように努力する).

本発表は, 以下の3部構成で行う. 第一部では, 強化学習の概要について, これまでの応用事例を用いて紹介する. 第二部では, 強化学習の数理的な基礎である動的計画法, 並びに代表的な強化学習アルゴリズムについて紹介する. 第三部では, セミパラメトリック統計推論の立場から強化学習を見直し, これまでに得た幾つかの重要な知見について紹介する.
[ 講演参考URL ]



16:30-18:00   数理科学研究科棟(駒場) 118号室
George Elliott 氏 (University of Toronto)
A survey of recent results on the classification of C*-algebras (ENGLISH)



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
Greg McShane 氏 (Institut Fourier, Grenoble)
Orthospectra and identities (ENGLISH)
[ 講演概要 ]
The orthospectra of a hyperbolic manifold with geodesic
boundary consists of the lengths of all geodesics perpendicular to the
We discuss the properties of the orthospectra, asymptotics, multiplicity
and identities due to Basmajian, Bridgeman and Calegari. We will give
a proof that the identities of Bridgeman and Calegari are the same.


16:30-18:00   数理科学研究科棟(駒場) 126号室
久保利久 氏 (東京大学 大学院 数理科学研究科)
The Dynkin index and conformally invariant systems of Heisenberg parabolic type (ENGLISH)
[ 講演概要 ]
Heisenberg parabolic subalgebraから構築されたconformally invariant
invariant systemを構築する際に重要な役割を果たしたが、ある二つの式の比率
具体的かつ一様な式をDynkin indexを交えて紹介する。



15:30-17:00   数理科学研究科棟(駒場) 122号室
大川 新之介 氏 (東京大学)
Derived category of smooth proper Deligne-Mumford stack with p_g>0 (JAPANESE)
[ 講演概要 ]
Semiorthogonal decomposition (SOD) of the derived category of coherent sheaves reflects interesting geometry of varieties (more generally stacks), such as minimal model program. We show that the global sections of the canonical line bundle (if exists) give restrictions on the possible form of SODs. As a special case, we see that the global generation of the canonical line bundle implies the non-existence of SODs. (joint work with Kotaro Kawatani)


16:30-17:30   数理科学研究科棟(駒場) 126号室
Thomas W. Roby 氏 (University of Connecticut)
Combinatorial Ergodicity (ENGLISH)
[ 講演概要 ]
Many cyclic actions $\\tau$ on a finite set $S$ of
combinatorial objects, along with many natural
statistics $\\phi$ on $S$, exhibit``combinatorial ergodicity'':
the average of $\\phi$ over each $\\tau$-orbit in $S$ is
the same as the average of $\\phi$ over the whole set $S$.
One example is the case where $S$ is the set of
length $n$ binary strings $a_{1}\\dots a_{n}$
with exactly $k$ 1's,
$\\tau$ is the map that cyclically rotates them,
and $\\phi$ is the number of \\textit{inversions}
(i.e, pairs $(a_{i},a_{j})=(1,0)$ for $iJ$ less than $j$).

This phenomenon was first noticed by Panyushev
in 2007 in the context of antichains in root posets;
Armstrong, Stump, and Thomas proved his
conjecture in 2011.
We describe a theoretical framework for results of this kind,
and discuss old and new results for products of two chains.

This is joint work with Jim Propp.



13:30-16:00   数理科学研究科棟(駒場) 123号室
竹森 翔 氏 (京都大学理学研究科) 13:30-14:30
degree n の Siegel-Eisenstein 級数の Fourier 係数について (JAPANESE)
[ 講演概要 ]
この話では,まず,あるdegree nのSiegel-Eisenstein級数G_{k,\\chi}を定義し,そのFourier係数の明示公式について述べます.このEisenstein級数G_{k,\\chi}は通常のSiegel-Eisenstein級数E_{k,\\chi}とは定義が違うのですが,G_{k,\\chi}のFourier係数の明示公式から,\\chiが特別な場合のE_{k,\\chi}のFourier係数の明示が得られます.
平田典子 氏 (日本大学理工学部) 15:00-16:00
多重対数関数と無理数性 (JAPANESE)
[ 講演概要 ]



17:00-18:00   数理科学研究科棟(駒場) 370号室
Oleg Emanouilov 氏 (Colorado State Univ.)
Inverse boundary value problem for Schroedinger equation in two dimensions (ENGLISH)
[ 講演概要 ]
We consider the Dirichlet-to-Neumann map for determining potential in two-dimensional Schroedinger equation. We relax the regularity condition on potentials and establish the uniqueness within L^p class with p > 2.



16:40-17:40   数理科学研究科棟(駒場) 056号室
Shane Kelly 氏 (Australian National University)
Voevodsky motives and a theorem of Gabber (ENGLISH)
[ 講演概要 ]
The assumption that the base field satisfies resolution of singularities litters Voevodsky's work on motives. While we don't have resolution of singularities in positive characteristic p, there is a theorem of Gabber on alterations which may be used as a substitute if we are willing to work with Z[1/p] coefficients. We will discuss how this theorem of Gabber may be applied in the context of Voevodsky's work and mention some consequences.


16:00-17:30   数理科学研究科棟(駒場) 128号室
関口 次郎 氏 (東京農工大学)
Free divisors, holonomic systems and algebraic Painlev\\'{e} sixth solutions (ENGLISH)
[ 講演概要 ]
In this talk, I will report an attempt to treat algebraic solutions of Painlev\\'{e} VI equation in a unified manner.
A classification of algebraic solutions of Painlev\\'{e} VI equation was accomplished by O. Lisovyy and Y. Tykhyy after efforts on the construction of such solutions by many authors, K. Iwasaki N. J. Hitchin, P. Boalch, B. Dubrovin, M. Mazzocco, A. V. Kitaev, R. Vidunas and others.
The outline of my approach is as follows.
Let $t$ be a variable and let $w$ be its algebraic function such that $w$ is a solution of Painlev\\'{e} sixth equation. Suppose that both $t$ and $w$ are rational functions of a parameter. Namely $(t,w)$ defines a rational curve.
(1) Find a polynomial $P(u)$ such that $t=\\frac{P(-u)}{P(u)}$.
(2) From $P(u)$, define a weighted homogeneous polynomial $f(x_1,x_2,x_3)=x_3f_1(x_1,x_2,x_3)$ of three variables $x_1,x_2,x_3$, where $(1,2,n)$ is the weight system of $(x_1,x_2,x_3)$ with $n=\\deg P(u)$. The hypersurface $D:f(x)=0$ is a free divisor in ${\\bf C}^3$. Note that $\\deg_{x_3}f_1=2$.
(3) Construct a holonomic system ${\\sl M}$ on ${\\bf C}^3$ of rank two with singularities along $D$.
(4) Construct an ordinary differential equation from the holonomic system ${\\sl M}$ with respect to $x_3$. This differential equation has three singular points $z_0,z_1,a_s$ in $x_3$-line.
(5) Putting $t=\\frac{z_1}{z_0},\\lambda=\\frac{a_s}{z_0}$, we conclude that $(t,\\lambda)$ is equivalent to the pair $(t,w)$.
Our study starts with showing the existence of $P(u)$ in (1). From the classification by Losovyy and Tykhyy, I find that the existence of $P(u)$ is guaranteed for Solutions III, IV, Solutions $k$ ($1\\le k\\le 21$, $k\\not= 4,13,14,20$) and Solution 30. We checked whether (1)-(5) are true or not in these cases separately and as a consequence (1)-(5) hold for the all these cases except Solutions 19, 21.



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
岡 睦雄 氏 (東京理科大学)
Contact structure of mixed links (JAPANESE)
[ 講演概要 ]
A strongly non-degenerate mixed function has a Milnor open book
structures on a sufficiently small sphere. We introduce the notion of
{\\em a holomorphic-like} mixed function
and we will show that a link defined by such a mixed function has a
canonical contact structure.
Then we will show that this contact structure for a certain
holomorphic-like mixed function
is carried by the Milnor open book.


16:30-18:00   数理科学研究科棟(駒場) 118号室
George Elliott 氏 (University of Toronto)
An introduction to C*-algebra classification theory (ENGLISH)


16:30-18:00   数理科学研究科棟(駒場) 128号室
菅 徹 氏 (東北大学)
2次元円環領域におけるLiouville-Gel\\'fand方程式の非球対称解の構造 (JAPANESE)
[ 講演概要 ]


17:00-18:30   数理科学研究科棟(駒場) 126号室
Eric Opdam 氏 (Universiteit van Amsterdam)
Dirac induction for graded affine Hecke algebras (ENGLISH)
[ 講演概要 ]
In recent joint work with Dan Ciubotaru and Peter Trapa we
constructed a model for the discrete series representations of graded affine Hecke algebras as the index of a Dirac operator.
We discuss the K-theoretic meaning of this result, and the remarkable relation between elliptic character theory of a Weyl group and the ordinary character theory of its Pin cover.



13:30-17:00   数理科学研究科棟(駒場) 128号室
和田出 秀光
(岐阜大学) 13:30-15:00
[ 講演概要 ]
澤野 嘉宏 氏 (首都大学東京
) 15:30-17:00
Boundedness of operators on Hardy spaces with variable exponents
[ 講演概要 ]
In this talk, as an off-spring, we will discuss the boundedness of various operators. Our plan of the talk is as follows:
First we recall the definition of Hardy spaces with variable exponents and then we describe the atomic decomposition.
Based upon the atomic decomposition, I define linear operators such as singular integral operators and commutators.
After the definition, I will state the boundedness results and outline the proof of the boundedness of these operators.



16:30-17:30   数理科学研究科棟(駒場) 370号室
M. Lavrentiev 氏 (Sobolev Institute of Mathematics)
Real time tsunami parameters evaluation (ENGLISH)
[ 講演概要 ]
We would like to propose several improvements to the existing software tools for tsunami modeling. Combination of optimaly located system of sensors with advantages of modern hardware architectures will make it possible to deliver calculated parameters of tsunami wave in 12-15 minutes after seismic event.

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