過去の記録 ~05/20本日 05/21 | 今後の予定 05/22~


13:30-15:00   数理科学研究科棟(駒場) 128号室
Jean-Dominique Deuschel 氏 (TU Berlin)
Mini course on the gradient models, I: Effective gradient models, definitions and examples
[ 講演概要 ]
We describe a phase separation in $R^{d+1}$ by an effective interface model with basis in $Z^d$ and height in $R$. We assume that the interaction potential depends only on the discrete gradient and that the a priori measure is the product Lebesgue measure. Note that this is an unbounded massless model with continuous symmetry and this implies that the interface is delocalized for the infinite model in lower lattice dimensions $d=1,2$. Instead of looking at the distribution of the height of the interface itself, we consider the measure on the height differences the so called gradient Gibbs measure, which exists in any dimensions. The gradient field must satisfy the loop condition, that is the sum of the gradient along any closed loop is zero, this implies a long range interaction with a slow decay of the correlations. We are interested in characterizing the ergodic components of this gradient field, in the decay of correlations, large deviations and continuous scaling limits. As an example we consider the harmonic or discrete gaussian free field with quadratic interactions.


16:40-18:10   数理科学研究科棟(駒場) 126号室
伊藤 敦 氏 (東大数理)
[ 講演概要 ]



16:20-17:50   数理科学研究科棟(駒場) 117号室
岡本龍明 氏 (NTT 情報流通プラットフォーム研究所 岡本特別研究室長)



15:30-17:00   数理科学研究科棟(駒場) 123号室
Claudio Landim 氏 (IMPA, Brazil)
Macroscopic fluctuation theory for nonequilibrium stationary states, Ⅱ


15:00-16:10   数理科学研究科棟(駒場) 128号室
矢田 和善 氏 (筑波大学大学院数理物質科学研究科)
[ 講演概要 ]

HDLSSデータに対して従来の統計手法を用いると,次元の呪いによって解析が上手くいかない.解決策の一つとして次元縮約法があり, その一つにPCAがある.高次元における従来型のPCAの漸近的性質は,正規性もしくは同等な仮定のもとで,先行研究が多数存在する. しかしながら,これら仮定は,HDLSSを研究する上で,厳しい制約にもなっている. Yata and Aoshimaの一連の研究は,この制約条件の枠を外すことから始まった.HDLSSにおける従来型PCAの限界は何か?推測が一致性をもつための標本数nと 次元数dの関係が,オーダー条件として明らかにされる.従来型PCAの限界を超える手法は何か?一つの実用的な方法として,クロス行列と呼ばれるデータの変換行列が導入され, この行列の特異値分解に基づいた新しいPCAが提案される.

[ 講演参考URL ]



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
Sergei Duzhin 氏 (Steklov Mathematical Institute, Petersburg Division)
Symbol of the Conway polynomial and Drinfeld associator
[ 講演概要 ]
The Magnus expansion is a universal finite type invariant of pure braids
with values in the space of horizontal chord diagrams. The Conway polynomial
composed with the short circuit map from braids to knots gives rise to a
series of finite type invariants of pure braids and thus factors through
the Magnus map. We describe explicitly the resulting mapping from horizontal
chord diagrams on 3 strands to univariante polynomials and evaluate it on
the Drinfeld associator obtaining a beautiful generating function whose
coefficients are integer combinations of multple zeta values.



15:30-17:00   数理科学研究科棟(駒場) 123号室
Claudio Landim 氏 (IMPA, Brazil)
Macroscopic fluctuation theory for nonequilibrium stationary states, I
[ 講演概要 ]
We present a review of recent work on the statistical mechanics of nonequilibrium processes based on the analysis of large deviations properties of microscopic systems. Stochastic lattice gases are non trivial models of such phenomena and can be studied rigorously providing a source of challenging mathematical problems. In this way, some principles of wide validity have been obtained leading to interesting physical consequences.



16:00-17:30   数理科学研究科棟(駒場) 002号室
Norayr MATEVOSYAN 氏 (ケンブリッジ大学・数理)
On a parabolic free boundary problem modelling price formation
[ 講演概要 ]
We will discuss existence and uniqueness of solutions for a one dimensional parabolic evolution equation with a free boundary. This problem was introduced by J.-M. Lasry and P.-L. Lions as description of the dynamical formation of the price of a trading good. Short time existence and uniqueness is established by a contraction argument. Then we discuss the issue of global-in time-extension of the local solution which is intimately connected to the regularity of the free boundary.
We also present numerical results.



16:30-18:00   数理科学研究科棟(駒場) 128号室
打越 敬祐 氏 (防衛大学校数学教育室)
[ 講演概要 ]



11:00-12:00   数理科学研究科棟(駒場) 123号室

Dinakar Ramakrishnan 氏 (カリフォルニア工科大学)
Modular forms and Calabi-Yau varieties



16:00-17:30   数理科学研究科棟(駒場) 002号室
Henrik SHAHGHOLIAN 氏 (王立工科大学・ストックホルム)
A two phase free boundary problem with applications in potential theory
[ 講演概要 ]
In this talk I will present some recent directions, still to be developed, in potential theory, that are connected to a two-phase free boundary problems. The potential theoretic topic that I will discuss is the so called Quadrature Domains.

The most simple free boundary/potential problem that we can present is the following. Given constants $a_\\pm, \\lambda_\\pm >0$ and two points $x^\\pm$ in ${\\bf R}^n$. Find a function $u$ such that
$$\\Delta u = \\left( \\lambda_+ \\chi_{\\{u>0 \\}} - a_+\\delta_{x^+}\\right) - \\left( \\lambda_- \\chi_{\\{u<0 \\}} - a_-\\delta_{x^-}\\right),$$
where $\\delta$ is the Dirac mass.

In general this problem is solvable for two Dirac masses. The requirement, somehow implicit in the above equation, is that the support of the measures (in this case the Dirac masses) is to be in included in the positivity and the negativity set (respectively).

In general this problem does not have a solution, and there some strong restrictions on the measures, in order to have some partial results.



15:00-16:00   数理科学研究科棟(駒場) 123号室
H.R.Thieme 氏 (Arizona State University)
Global compact attractors and their tripartition under persistence (ENGLISH)
[ 講演概要 ]
The study of the dynamics of a semiflow (inertial manifolds, persistence) is largely facilitated if there is a global compact attractor, i.e. a compact invariant subset which attracts a sufficiently broad class of subsets of the state space.
Unfortunately, there in no uniform use of the concept of a global compact attractor in the literature: it has been used for a compact attractor of points, compact attractor of neighborhoods of compact sets, and compact attractor of bounded sets.
Persistence theory allows to discuss the long-term survival of populations in a dynamical systems framework. There is a two-way interaction between persistence and global compact attractors. On the one hand, the existence of a compact attractor of points helps to establish the persistence of the semiflow. On the other hand, the global attractor of a uniformly persistent semiflow divides into three invariant parts: an extinction attractor, a persistence attractor, and a set of orbits that connect the extinction to the persistence attractor. The persistence attractor has further interesting properties like local stability and connectedness. Examples are presented where the persistence attractor can be used to prove the global stability of the persistence equilibrium. (joint work with Hal L. Smith)


16:15-17:15   数理科学研究科棟(駒場) 123号室
Glenn Webb 氏 (Vanderbilt University)
Analysis of a Model for Transfer Phenomena in Biological Populations (ENGLISH)
[ 講演概要 ]
We study the problem of transfer in a population structured by a continuum variable corresponding to the quantity being transferred. The transfer of the quantity occurs between individuals according to specified rules. The model is of Boltzmann type with kernel corresponding to the transfer process. We prove that the transfer process preserves total mass of the transferred quantity and the solutions of the simple model converge weakly to Radon measures. We generalize the model by introducing proliferation of individuals and production and diffusion of the transferable quantity. It is shown that the generalized model admits a globally asymptotically stable steady state, provided that transfer is sufficiently small. We discuss an application of our model to cancer cell populations, in which individual cells exchange the surface protein P-glycoprotein, an important factor in acquired multidrug resistance against cancer chemotherapy.



17:00-18:30   数理科学研究科棟(駒場) 056号室
Marek Bozejko 氏 (University of Wroclaw)
Generalized Gaussian field, theta function of Jacobi and functor of second quantization



16:30-18:00   数理科学研究科棟(駒場) 002号室
Matthias Schuett 氏 (Leibniz University Hannover)
Arithmetic of K3 surfaces
[ 講演概要 ]
This talk aims to review recent developments in the arithmetic of K3 surfaces, with emphasis on singular K3 surfaces.
We will consider in particular modularity, Galois action on Neron-Severi groups and behaviour in families.



10:00-16:30   数理科学研究科棟(駒場) 002号室
Sigurdur Helgason 氏 (MIT) 10:00-11:00
Radon Transform and some Applications
Fulton G. Gonzalez 氏 (Tufts University) 11:20-12:20
Multitemporal Wave Equations: Mean Value Solutins
Angela Pasquale 氏 (Universite Metz) 14:00-15:00
Analytic continuation of the resolvent of the Laplacian in the Euclidean settings
[ 講演概要 ]
We discuss the analytic continuation of the resolvent of the Laplace operator on symmetric spaces of the Euclidean type and some generalizations to the rational Dunkl setting.
Henrik Schlichtkrull 氏 (University of Copenhagen) 15:30-16:30
Decay of smooth vectors for regular representations
[ 講演概要 ]
Let $G/H$ be a homogeneous space of a Lie group, and consider the regular representation $L$ of $G$ on $E=L^p(G/H)$. A smooth vector for $L$ is a function $f$ in $E$ such that $g$ mapsto $L(g)f$ is smooth, $G$ to $E$. We investigate circumstances under which all such functions decay at infinity (jt with B. Krotz)



16:30-17:30   数理科学研究科棟(駒場) 117号室
Fabien Trihan 氏 (Nottingham大学)
On the $p$-parity conjecture in the function field case
[ 講演概要 ]
Let $F$ be a function field in one variable with field of constant a finite field of characteristic $p>0$. Let $E/F$ be an elliptic curve over $F$. We show that the order of the Hasse-Weil $L$-function of $E/F$ at $s=1$ and the corank of the $p$-Selmer group of $E/F$ have the same parity (joint work with C. Wuthrich).



11:00-15:45   数理科学研究科棟(駒場) 002号室
東京大学グローバルCOE事業の一環として,サマースクール『非可積分系におけるソリトンの振舞いと安定性』を開催します. チュートリアル形式の講義ですので,非専門家や若手を含む,多くの�
水町 徹 氏 (九州大学) 11:00-12:00
Frank Merle 氏 (Cergy Pontoise 大学/IHES) 13:30-14:30
Dynamics of solitons in non-integrable systemsⅤ
Frank Merle 氏 (Cergy Pontoise 大学/IHES) 14:45-15:45
Dynamics of solitons in non-integrable systemsⅥ
[ 講演参考URL ]



11:00-17:15   数理科学研究科棟(駒場) 002号室
東京大学グローバルCOE事業の一環として,サマースクール『非可積分系におけるソリトンの振舞いと安定性』を開催します. チュートリアル形式の講義ですので,非専門家や若手を含む,多くの�
水町 徹 氏 (京都大学) 11:00-12:00
[ 講演概要 ]
KdV方程式をはじめとする長波長近似の非線形分散型方程式は,水面波の運動やプラズマ中のイオンの運動を記述することで知られている. KdV方程式のソリトン解は安定的に伝播することが知られていたが,近年変分法に基づいたアプローチで非可積分系のモデルの場合にもソリトン解とよく似た解が安定的に存在することが証明された.第1回目の講演ではに変分原理に基づいた安定性の結果について概説し,次にFermi-Pasta-Ulam格子やある種の流体のbidirectional modelなど変分原理から安定性がうまく説明できないモデルの場合について述べる.
Frank Merle 氏 (Cergy Pontoise 大学/IHES) 13:30-14:30
Dynamics of solitons in non-integrable systemsⅢ
Frank Merle 氏 (Cergy Pontoise 大学/IHES) 14:45-15:45
Dynamics of solitons in non-integrable systemsⅣ
中西 賢次 氏 (九州大学) 16:15-17:15
[ 講演参考URL ]



13:30-17:15   数理科学研究科棟(駒場) 002号室
東京大学グローバルCOE事業の一環として,サマースクール『非可積分系におけるソリトンの振舞いと安定性』を開催します. チュートリアル形式の講義ですので,非専門家や若手を含む,多くの�
Frank Merle 氏 (Cergy Pontoise 大学/IHES) 13:30-14:30
Dynamics of solitons in non-integrable systemsⅠ
[ 講演概要 ]
完全可積分系であるKdV方程式においては,多重ソリトン解の構造はすでに詳しく解明されており,ソリトンどうしが衝突した後,各ソリトンの形状がすぐに元通りに復元するなどの性質もよく知られている.しかし方程式中の指数を変えて得られる一般化KdV方程式の場合は,非可積分系であるため,多重ソリトン解の便利な表示式は存在せず,ソリトンどうしの衝突後に何が起こるのか,理論的には未解明であった.Merle氏は,最近Yvon Martel氏と共同でこの問題を解決し,衝突後にわずかな欠損が生じるもののソリトンの形状が見事に復元することを証明するとともに,大きなソリトンが微小なソリトンと衝突した際に生じる位相(phase)のズレに関して, KdV方程式の場合と全く違う現象が起こることも明らかにした.
Frank Merle 氏 (Cergy Pontoise 大学/IHES) 14:45-15:45
Dynamics of solitons in non-integrable systemsⅡ
中西 賢次 氏 (京都大学) 16:15-17:15
[ 講演概要 ]
[ 講演参考URL ]



14:00-15:15   数理科学研究科棟(駒場) 123号室
野澤 啓 氏 (東京大学大学院数理科学研究科)
『Five dimensional K-contact Manifolds of rank 2(階数2の5次元K接触多様体について)』

Kavli IPMU Komaba Seminar

17:00-18:30   数理科学研究科棟(駒場) 002号室
Misha Verbitsky 氏 (ITEP Moscow/IPMU)
Mapping class group for hyperkaehler manifolds
[ 講演概要 ]
A mapping class group is a group of orientation-preserving
diffeomorphisms up to isotopy. I explain how to compute a
mapping class group of a hyperkaehler manifold. It is
commensurable to an arithmetic lattice in a Lie group
$SO(n-3,3)$. This makes it possible to state and prove a
new version of Torelli theorem.



16:30-17:30   数理科学研究科棟(駒場) 123号室
お茶&Coffee&お菓子: 16:00~16:30 (コモンルーム)
Carlos Simpson 氏 (CNRS, University of Nice)
Differential equations and the topology of algebraic varieties
[ 講演概要 ]
The study of the topology of complex algebraic varieties makes use of differential equations in several different ways. The classical notion of variation of Hodge structure contains, on the one hand, the Gauss-Manin differential equations, on the other hand Hodge metric data which satisfy harmonic bundle equations. These two aspects persist in the study of arbitrary representations of the fundamental group. Combining them leads to a notion of ``Hodge structure'' on the space of representations. This can be extended to the higher homotopical structure of a variety, by using ideas of ``shape'' and nonabelian cohomology.


13:00-15:30   数理科学研究科棟(駒場) 056号室
武部尚志 氏 (Faculty of Math, Higher School of Economics, Moscow) 13:00-14:00
On recursion relation of the KP hierarchy
[ 講演概要 ]
This talk is based on an ongoing project in collaboration with Takasaki and Tsuchiya. Our goal is to reconstruct and generalise results by Eynard et al. from the standpoint of the integrable systems. Eynard, Orantin and their collaborators found "topological recursion formulae" to describe partition functions and correlation functions of the matrix models, topological string theories etc., using simple algebro-geometric data called "spectral curves". On the other hand, it is well known that the partition functions of those theories are tau functions of integrable hierarchies.
We have found that any solution of the KP hierarchy (with an asymptotic expansion parameter h) can be recovered by recursion relations from its "dispersionless" part (which corresponds to the genus zero part in topological theories) and a quantised contact transformation (which corresponds to the string equations) specifying the solution.
高崎金久 氏 (京大人間) 14:30-15:30
[ 講演概要 ]
をもち、それ以外では単純分岐点のみもつような n 次分岐被覆を考える。
満たす関係式 (拘束条件) を紹介し、そこから導かれる帰結を探る。



16:30-18:00   数理科学研究科棟(駒場) 056号室
Catherine Oikonomides 氏 (慶応大理工)
Cyclic cohomology and the Novikov conjecture

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