講演会

過去の記録 ~02/23次回の予定今後の予定 02/24~


過去の記録

2017年10月25日(水)

11:00-12:00   数理科学研究科棟(駒場) 128号室
Ahmed Abbes 氏 (CNRS/IHES)
On Faltings' main comparison theorem in p-adic Hodge theory : the relative case (ENGLISH)
[ 講演概要 ]
In the appendix of his 2002 Asterisque article, Faltings roughly sketched a proof of a relative version of his main comparison theorem in p-adic Hodge theory. I will briefly review the absolute case and then explain some of the key new inputs for the proof of the relative case (joint work with Michel Gros).

2017年10月17日(火)

17:00-18:00   数理科学研究科棟(駒場) 128号室
Guoniu Han 氏 (Université de Strasbourg/CNRS)
Integer partitions and hook length formulas (ENGLISH)
[ 講演概要 ]
Integer partitions were first studied by Euler.
The Ferrers diagram of an integer partition is a very useful tool for
visualizing partitions. A Ferrers diagram is turned into a Young tableau
by filling each cell with a unique integer satisfying some conditions.
The number of Young tableaux is given by the famous hook length formula,
discovered by Frame-Robinson-Thrall.
In this talk, we introduce the hook length expansion technique and
explain how to find old and new hook length formulas for integer
partitions. In particular, we derive an expansion formula for the
powers of the Euler Product in terms of hook lengths, which is also
discovered by Nekrasov-Okounkov and Westburg. We obtain an extension
by adding two more parameters. It appears to be a discrete
interpolation between the Macdonald identities and the generating
function for t-cores. Several other summations involving hook length,
in particular, the Okada-Panova formula, will also be discussed.
[ 講演参考URL ]
www-irma.u-strasbg.fr/~guoniu/

2017年10月11日(水)

11:00-12:00   数理科学研究科棟(駒場) 128号室
Ahmed Abbes 氏 (CNRS/IHES)
On Faltings' main comparison theorem in p-adic Hodge theory : the relative case (ENGLISH)
[ 講演概要 ]
In the appendix of his 2002 Asterisque article, Faltings roughly sketched a proof of a relative version of his main comparison theorem in p-adic Hodge theory. I will briefly review the absolute case and then explain some of the key new inputs for the proof of the relative case (joint work with Michel Gros).

2017年09月11日(月)

15:30-16:30   数理科学研究科棟(駒場) 002号室
Jean Zinn-Justin 氏 (CEA Saclay)
3D field theories with Chern-Simons term for large N in the Weyl gauge
(ENGLISH)
[ 講演概要 ]
ADS/CFT correspondance has led to a number of conjectures concerning, conformal invariant, U(N) symmetric 3D field theories with Chern-Simons term for N large. An example is boson-fermion duality. This has prompted a number of calculations to shed extra light on the ADS/CFT correspondance.
We study here the example of gauge invariant fermion matter coupled to a Chern-Simons term. In contrast with previous calculations, which employ the light-cone gauge, we use the more conventional temporal gauge. We calculate several gauge invariant correlation functions. We consider general massive matter and determine the conditions for conformal invariance. We compare massless results with previous calculations, providing a check of gauge independence.
We examine also the possibility of spontaneous breaking of scale invariance and show that this requires the addition of an auxiliary scalar field.
Our method is based on field integral and steepest descent. The saddle point equations involve non-local fields and take the form of a set of integral equations that we solve exactly.

2017年05月23日(火)

17:00-18:00   数理科学研究科棟(駒場) 126号室
講演後の質疑応答の状況によっては、終了時間が多少遅れるかもしれません。
Frédéric Jouhet 氏 (Université Claude Bernard Lyon 1 / Institut Camille Jordan)
Enumeration of fully commutative elements in classical Coxeter groups (English)
[ 講演概要 ]
An element of a Coxeter group W is fully commutative if any two of its reduced decompositions are related by a series of transpositions of adjacent commuting generators. They index naturally a basis of the (generalized) Temperley-Lieb algebra associated with W. In this talk, focusing on the (affine) type A, I will describe how to
enumerate these elements according to their Coxeter length, in all classical finite and affine Coxeter groups. The methods, which generalize previous work of Stembridge,
involve many combinatorial objects, such as heaps, walks, or parallelogram
polyominoes. This talk is based on joint works with R. Biagioli, M. Bousquet-Mélou and
P. Nadeau.
[ 講演参考URL ]
http://math.univ-lyon1.fr/homes-www/jouhet/

2015年07月28日(火)

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.

2015年05月21日(木)

16:00-17:00   数理科学研究科棟(駒場) 056号室
Tea:15:30~16:00 コモンルーム
Gunnar Carlsson  氏 (Stanford University, Ayasdi INC)
The Shape of Data
(ENGLISH)
[ 講演概要 ]
There is a tremendous amount of attention being paid to the notion of
"Big Data". In many situations, however, the problem is not so much the
size of the data but rather its complexity. This observation shows that
it is now important to find methods for representing complex data in a
compressed and understandable fashion. Representing data by shapes
turns out to be useful in many situations, and therefore topology, the
mathematical sub discipline which studies shape, becomes quite
relevant. There is now a collection of methods based on topology for
analyzing complex data, and in this talk we will discuss these methods,
with numerous examples.
[ 講演参考URL ]
http://faculty.ms.u-tokyo.ac.jp/Carlsson.html

2014年12月03日(水)

16:30-17:30   数理科学研究科棟(駒場) 128号室
Xavier Cabre 氏 (ICREA and UPC, Barcelona)
New isoperimetric inequalities with densities, part II: Detailed proofs and related works (ENGLISH)
[ 講演概要 ]
This is a sequel to the Tuesday Analysis Seminar on December 2 by the same speaker.
In joint works with X. Ros-Oton and J. Serra, the study of the regularity of stable solutions to reaction-diffusion problems has led us to certain Sobolev and isoperimetric inequalities with weights. We will present our results in these new isoperimetric inequalities with the best constant, that we establish via the ABP method.
More precisely, we obtain a new family of sharp isoperimetric inequalities with weights (or densities) in open convex cones of R^n. Our results apply to all nonnegative homogeneous weights satisfying a concavity condition in the cone. Surprisingly, even that our weights are not radially symmetric, Euclidean balls centered at the origin (intersected with the cone) minimize the weighted isoperimetric quotient. As a particular case of our results, we provide with new proofs of classical results such as the Wulff inequality and the isoperimetric inequality in convex cones of Lions and Pacella. Furthermore, we also study the anisotropic isoperimetric problem for the same class of weights and we prove that the Wulff shape always minimizes the anisotropic weighted perimeter under the weighted volume constraint.

2014年11月26日(水)

16:00-17:00   数理科学研究科棟(駒場) 123号室
Mykhaylo Shkolnikov 氏 (Princeton University)
Intertwinings, wave equations and beta ensembles (ENGLISH)
[ 講演概要 ]
We will discuss a general theory of intertwined diffusion processes of any dimension. Intertwined processes arise in many different contexts in probability theory, most notably in the study of random matrices, random polymers and path decompositions of Brownian motion. Recently, they turned out to be also closely related to wave equations and more general hyperbolic partial differential equations. The talk will be devoted to this recent development, as well as an algebraic perspective on intertwinings which, in particular, gives rise to a novel intertwining in beta random matrix theory. Based on joint works with Vadim Gorin and Soumik Pal.

2014年09月04日(木)

12:10-13:00   数理科学研究科棟(駒場) 470号室
Samuli Siltanen 氏 (University of Helsinki, Finland)
X-ray imaging of moving objects (ENGLISH)

2014年06月10日(火)

14:40-16:10   数理科学研究科棟(駒場) 056号室
Sergei Duzhin 氏 (Steklov Institute of Mathematics)
Bipartite knots (ENGLISH)
[ 講演概要 ]
We give a solution to a part of Problem 1.60 in Kirby's list of open
problems in topology thus proving a conjecture raised in 1987 by
J.Przytycki. A knot is said to be bipartite if it has a "matched" diagram,
that is, a plane diagram that has an even number of crossings which can be
split into pairs that look like a simple braid on two strands with two
crossings. The conjecture was that there exist knots that do not have such
diagrams. I will prove this fact using higher Alexander ideals.
This talk is based on a joint work with my student M.Shkolnikov

2014年05月15日(木)

16:30-17:30   数理科学研究科棟(駒場) 050号室
Cédric Villani 氏 (Université de Lyon, Institut Henri Poincaré)
Synthetic theory of Ricci curvature
― When Monge, Riemann and Boltzmann meet ― (ENGLISH)
[ 講演概要 ]
Optimal transport theory, non-Euclidean geometry and statistical physics met fifteen years ago with the discovery that Ricci curvature can be studied quantitatively thanks to entropy and
Monge-Kantorovich transport.
This unexpected encounter was very fruitful, leading to progress in each of these fields.
[ 講演参考URL ]
http://faculty.ms.u-tokyo.ac.jp/Villani.html

2014年03月13日(木)

10:15-11:45   数理科学研究科棟(駒場) 470号室
Michele Triestino 氏 (Ecole Normale Superieure de Lyon)
Almost sure triviality of the $C^1$-centralizer of random circle diffeomorphisms with periodic points (ENGLISH)
[ 講演概要 ]
By the end of the 80s, Malliavin and Shavgulidze introduced a measure on the space of C^1 circle diffeomorphisms which carries many interesting features. Perhaps the most interesting aspect is that it can be considered as an analog of the Haar measure for the group Diff^1_+(S^1).
The nature of this measure has been mostly investigated in connection to representation theory.
For people working in dynamical systems, the MS measure offers a way to quantify dynamical phenomena: for example, which is the probability that a random diffeomorphism is irrational? Even if this question have occupied my mind for a long time, it remains still unanswered, as many other interesting ones. However, it is possible to understand precisely what are the typical features of a diffeomorphism with periodic points.

2014年03月12日(水)

10:15-11:45   数理科学研究科棟(駒場) 470号室
Michele Triestino 氏 (Ecole Normale Superieure de Lyon)
Invariant distributions for circle diffeomorphisms of
irrational rotation number and low regularity (ENGLISH)
[ 講演概要 ]
The main inspiration of this joint work with Andrés Navas is the beautiful result of Ávila and Kocsard: if f is a C^\\infty circle diffeomorphism of irrational rotation number, then the unique invariant probability measure is also the unique (up to rescaling) invariant distribution.
Using conceptual geometric arguments (Hahn-Banach...), we investigate the uniqueness of invariant distributions for C^1 circle diffeomorphisms of irrational rotation number, with particular attention to sharp regularity.
We prove that If the diffeomorphism is C^{1+bv}, then there is a unique invariant distribution of order 1. On the other side, examples by Douady and Yoccoz, and by Kodama and Matsumoto exhibit differentiable dynamical systems for which the uniqueness does not hold.

2014年03月10日(月)

15:15-16:45   数理科学研究科棟(駒場) 123号室
Marielle Simon 氏 (ENS Lyon, UMPA)
Energy fluctuations in the disordered harmonic chain (ENGLISH)
[ 講演概要 ]
We study the energy diffusion in the disordered harmonic chain of oscillators: the usual Hamiltonian dynamics is provided with random masses and perturbed by a degenerate energy conserving noise. After rescaling space and time diffusively, we prove that energy fluctuations evolve following an infinite dimensional linear stochastic differential equation driven by the linearized heat equation. We also give variational expressions for the thermal diffusivity and an equivalent definition through the Green-Kubo formula. Since the model is non gradient, and the perturbation is very degenerate, the standard Varadhan's approach is reviewed under new perspectives.

2014年02月17日(月)

16:30-17:30   数理科学研究科棟(駒場) 002号室
Canceled!! (本人の都合により,講演は取りやめとなりました.)
Ratnasingham Shivaji 氏 (The University of North Carolina at Greensboro)
Canceled!! (ENGLISH)
[ 講演概要 ]
Canceled!!

2013年12月19日(木)

17:00-18:00   数理科学研究科棟(駒場) 270号室
Guanghui Hu 氏 (WIAS, Germany)
Inverse elastic wave scattering from rigid diffraction gratings (ENGLISH)
[ 講演概要 ]
In recent years, Schwarz reflection principles have been used to prove uniqueness in inverse scattering by bounded obstacles and unbounded periodic structures of polygonal or polyhedral type with only one or several incident plane waves.
Such a principle for the Navier equation is established by far only underthe third or fourth kind boundary conditions, and still remains unknown in the more practical case of the Dirichlet boundary condition.
In this talk we will discuss the uniqueness in inverse elastic scattering from rigid diffraction gratings of polygonal type, where the total displacement vanishes on the scattering surface. Mathematically, this can be modeled by the Dirichlet boundary value problem for the Navier equation in periodic structures. We prove that such diffraction gratings can be uniquely
determined from the near-field data corresponding to a finite number of incident elastic plane waves.
This is a joint work with J. Elschner and M. Yamamoto.

2013年07月25日(木)

13:00-15:00   数理科学研究科棟(駒場) 126号室
Joergen E Andersen 氏 (Centre for Quantum Geometry of Moduli Spaces (QGM), Aarhus University, Denmark
)
モジュライ構造とChern-Simons量子場理論 (ENGLISH)

2013年07月23日(火)

13:00-15:00   数理科学研究科棟(駒場) 002号室
Joergen E Andersen 氏 (Centre for Quantum Geometry of Moduli Spaces (QGM), Aarhus University, Denmark
)
モジュライ構造と蛋白質構造のクラスタリング (ENGLISH)

2013年07月22日(月)

13:00-15:00   数理科学研究科棟(駒場) 126号室
Joergen E Andersen 氏 (Centre for Quantum Geometry of Moduli Spaces (QGM), Aarhus University, Denmark
)
RNA構造のモジュライ構造とエネルギー計算 (ENGLISH)

2013年07月08日(月)

10:40-12:10   数理科学研究科棟(駒場) 128号室
出原浩史 氏 (明治大学 先端数理科学インスティテュート)
生物の集合形成メカニズム:ミクロとマクロの視点から (JAPANESE)
[ 講演概要 ]
自然界では集合し生活する生物が数多くいる.そのような生物種のダイナミクスを表現するためにミクロレベルの視点からランダムウォークに基づく粒子モデルがしばしば提唱される. 一方,生物の個体群密度を考慮した場合, そのダイナミクスはマクロレベルの偏微分方程式モデルとして表現される.
このように着目する視点によって提唱されるモデルは異なる. 本講演では, 生物の集合現象を例に,ミクロレベルでの粒子モデルとマクロレベルでの偏微分方程式モデルの間の関係を紹介したい.

2013年06月13日(木)

16:30-18:00   数理科学研究科棟(駒場) 117号室
望月 新一 氏 (京都大学数理解析研究所)
宇宙際タイヒミューラー理論への誘(いざな)い 《拡大版》
(JAPANESE)

2013年05月24日(金)

16:30-18:00   数理科学研究科棟(駒場) 002号室
5/10(金) 5/14(火) 5/21(火) 5/24(金)の4回連続講演の最終回です。

Laurent Lafforgue 氏 (IHES)
Kernels of Langlands' automorphic transfer and non-linear Poisson formulas (JAPANESE)

2013年05月21日(火)

16:30-18:00   数理科学研究科棟(駒場) 118号室
5/10(金) 5/14(火) 5/21(火) 5/24(金)の4回連続講演です。部屋と時間は毎回同じです
Laurent Lafforgue 氏 (IHES)
Kernels of Langlands' automorphic transfer and non-linear Poisson formulas (ENGLISH)

2013年05月14日(火)

16:30-18:00   数理科学研究科棟(駒場) 118号室
5/10(金) 5/14(火) 5/21(火) 5/24(金)の4回連続講演です。部屋と時間は毎回同じです

Laurent Lafforgue 氏 (IHES)
Kernels of Langlands' automorphic transfer and non-linear Poisson formulas (ENGLISH)

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