Seminar information archive
Seminar information archive ~02/15|Today's seminar 02/16 | Future seminars 02/17~
Tuesday Seminar on Topology
Ken'ichi Yoshida (The University of Tokyo)
Union of 3-punctured spheres in a hyperbolic 3-manifold (JAPANESE)
An essential 3-punctured sphere in a hyperbolic 3-manifold is isotopic to a totally geodesic one. We will classify the topological types for components of union of the totally geodesic 3-punctured spheres in an orientable hyperbolic 3-manifold. There are special types each of which appears in precisely one manifold.
Classical Analysis
David Sauzin (CNRS)
Introduction to resurgence on the example of saddle-node singularities (ENGLISH)
Divergent power series naturally appear when solving such an elementary differential equation as x^2 dy = (x+y) dx, which is the simplest example of saddle-node singularity. I will discuss the formal classification of saddle-node singularities and illustrate on that case Ecalle's resurgence theory, which allows one to analyse the divergence of the formal solutions. One can also deal with resonant saddle-node singularities with one more dimension, a situation which covers the local study at infinity of some Painlevé equations.
2016/12/05
Seminar on Geometric Complex Analysis
Takahiro Oba (Tokyo Institute of Technology )
(JAPANESE)
Operator Algebra Seminars
Shuhei Masumoto (Univ.Tokyo)
On a generalized Fraïssé limit construction (English)
2016/12/01
Seminar on Probability and Statistics
Ciprian Tudor (Université Lille 1)
On the determinant of the Malliavin matrix and density of random vector on Wiener chaos
A well-known problem in Malliavin calculus concerns the relation between the determinant of the Malliavin matrix of a random vector and the determinant of its covariance matrix. We give an explicit relation between these two determinants for couples of random vectors of multiple integrals. In particular, if the multiple integrals are of the same order, we prove that two random variables in the same Wiener chaos either admit a joint density, either are proportional and that the result is not true for random variables in Wiener chaoses of different orders.
2016/11/29
Algebraic Geometry Seminar
Karl Schwede (University of Utah)
Etale fundamental groups of F-regular schemes (English)
I will discuss recent work studying etale fundamental groups of the regular locus of F-regular schemes. I will describe how to use F-signature to bound the size of the fundamental group of an F-regular scheme, similar to a result of Xu. I will then discuss a recent extension showing that every F-regular scheme X has a finite cover Y, etale over the regular lcous of X, so that the etale fundamental groups of Y and the regular locus of Y agree. This is analogous to results of Greb-Kebekus-Peternell.
All the work discussed is joint with Carvajal-Rojas and Tucker or with with Bhatt, Carvajal-Rojas, Graf and Tucker.
Tuesday Seminar on Topology
Hayato Chiba (Kyushu University)
Generalized spectral theory and its application to coupled oscillators on networks (JAPANESE)
For a system of large coupled oscillators on networks, we show that the transition from the de-synchronous state to the synchronization occurs as the coupling strength increases. For the proof, the generalized spectral theory of linear operators is employed.
Tuesday Seminar of Analysis
Naotaka Shouji (Graduate School of Pure and Applied Sciences, University of Tsukuba)
Interior transmission eigenvalue problems on manifolds (Japanese)
2016/11/28
Seminar on Geometric Complex Analysis
Satoshi Nakamura (Tohoku University)
(JAPANESE)
Operator Algebra Seminars
Takahiro Hasebe (Hokkaido University)
Fock space deformed by Coxeter groups (English)
Discrete mathematical modelling seminar
Alfred Ramani (IMNC, Universite de Paris 7 et 11)
Who cares about integrability ? (ENGLISH)
I will start my talk with an introduction to integrability of continuous systems. Why is it important? Is it possible to give a definition of integrability which will satisfy everybody? (Short answer: No). I will then present the most salient discoveries of integrable systems, from Newton to Toda. Next I will address the question of discrete integrability. This will lead naturally to the question of discretisation (of continuous systems) and its importance in modelling. I will deal with the construction of integrable discretisations of continuous integrable systems and introduce the singularity confinement discrete integrability criterion. The final part of my talk will be devoted to discrete Painlevé equations. Due to obvious time constraints I will concentrate on one special class of these equations, namely those associated to the E8 affine Weyl group. I will present a succinct summary of our recent results as well as indications for future investigations.
2016/11/25
FMSP Lectures
Arthur Ogus (University of California, Berkeley)
Introduction to Logarithmic Geometry V (ENGLISH)
Logarithmic Geometry was invented (or discovered) in the 1980's, with crucial ideas contributed by Deligne, Faltings, Fontaine, Illusie, and especially K. Kato. It provides a systematic framework for the study of the related phenomena of compactification and degeneration in algebraic and arithmetic geometry, with applications to number theory. I will attempt to explain the main ideas and foundations of Kato's version of log geometry, with an emphasis on its geometric and topological aspects.
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Ogus.pdf
Colloquium
Tsuyoshi Yoneda (Graduate School of Mathematical Sciences, The University of Tokyo)
An instability mechanism of pulsatile flow along particle trajectories for the axisymmetric Euler equations
[ Reference URL ]
https://www.ms.u-tokyo.ac.jp/~yoneda/index.html
2016/11/22
PDE Real Analysis Seminar
Yannick Sire (Johns Hopkins University)
De Giorgi conjecture and minimal surfaces for integro-differential operators (English)
I will review the classical De Giorgi conjecture and its link with minimal surfaces. Then I will move on recent results for flatness of level sets of solutions of semi linear equations involving anomalous diffusion. First I will deal with the fractional laplacian; second with quite general integral operators in 2 dimensions.
Tuesday Seminar on Topology
Takahito Naito (The University of Tokyo)
Sullivan's coproduct on the reduced loop homology (JAPANESE)
In string topology, Sullivan introduced a coproduct on the reduced loop homology and showed that the homology has an infinitesimal bialgebra structure with respect to the coproduct and Chas-Sullivan loop product. In this talk, I will give a homotopy theoretic description of Sullivan's coproduct. By using the description, we obtain some computational examples of the structure over the rational number field. Moreover, I will also discuss a based loop space version of the coproduct.
2016/11/21
FMSP Lectures
Arthur Ogus (University of California, Berkeley)
Introduction to Logarithmic Geometry IV (ENGLISH)
Logarithmic Geometry was invented (or discovered) in the 1980's, with crucial ideas contributed by Deligne, Faltings, Fontaine, Illusie, and especially K. Kato. It provides a systematic framework for the study of the related phenomena of compactification and degeneration in algebraic and arithmetic geometry, with applications to number theory. I will attempt to explain the main ideas and foundations of Kato's version of log geometry, with an emphasis on its geometric and topological aspects.
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Ogus.pdf
Seminar on Geometric Complex Analysis
Toshihiro Nose (Fukuoka Institute of Technology)
(JAPANESE)
Numerical Analysis Seminar
Sotirios E. Notaris (National and Kapodistrian University of Athens)
Gauss-Kronrod quadrature formulae (English)
In 1964, the Russian mathematician A.S. Kronrod, in an attempt to estimate practically the error term of the well-known Gauss quadrature formula, presented a new quadrature rule, which since then bears his name. It turns out that the new rule was related to some polynomials that Stieltjes developed some 70 years earlier, through his work on continued fractions and the moment problem. We give an overview of the Gauss-Kronrod quadrature formulae, which are interesting from both the mathematical and the applicable point of view.
The talk will be expository without requiring any previous knowledge of numerical integration.
Operator Algebra Seminars
Narutaka Ozawa (RIMS, Kyoto Univ.)
Finite-dimensional representations constructed from random walks (joint work with A. Erschler)
Tokyo Probability Seminar
Yukio Nagahata (Faculty of Engineering, Niigata University)
On scaling limit of a cost in adhoc network model
2016/11/19
Discrete mathematical modelling seminar
Takayuki Hasegawa (Toyama National College of Technology) 14:00-15:15
(JAPANESE)
Hironobu Fujishima (Canon) 15:45-17:00
(JAPANESE)
2016/11/18
FMSP Lectures
Arthur Ogus (University of California, Berkeley)
Introduction to Logarithmic Geometry III (ENGLISH)
Logarithmic Geometry was invented (or discovered) in the 1980's, with crucial ideas contributed by Deligne, Faltings, Fontaine, Illusie, and especially K. Kato. It provides a systematic framework for the study of the related phenomena of compactification and degeneration in algebraic and arithmetic geometry, with applications to number theory. I will attempt to explain the main ideas and foundations of Kato's version of log geometry, with an emphasis on its geometric and topological aspects.
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Ogus.pdf
2016/11/17
Seminar on Mathematics for various disciplines
Qing Liu (Fukuoka University)
Convexity preserving properties for nonlinear evolution equations (English)
It is well known that convexity of solutions to a general class of nonlinear parabolic equations in the Euclidean space is preserved as time develops. In this talk, we first revisit this property for the normalized infinity Laplace equation and the curvature flow equation by introducing an alternative approach based on discrete game theory. We then extend our discussion to Hamilton-Jacobi equations in the Heisenberg group and in more general geodesic metric spaces.
2016/11/16
FMSP Lectures
Arthur Ogus (University of California, Berkeley)
Introduction to Logarithmic Geometry II (ENGLISH)
Logarithmic Geometry was invented (or discovered) in the 1980's, with crucial ideas contributed by Deligne, Faltings, Fontaine, Illusie, and especially K. Kato. It provides a systematic framework for the study of the related phenomena of compactification and degeneration in algebraic and arithmetic geometry, with applications to number theory. I will attempt to explain the main ideas and foundations of Kato's version of log geometry, with an emphasis on its geometric and topological aspects.
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Ogus.pdf
2016/11/15
Tuesday Seminar on Topology
Takuya Sakasai (The University of Tokyo)
Cohomology of the moduli space of graphs and groups of homology cobordisms of surfaces (JAPANESE)
We construct an abelian quotient of the symplectic derivation Lie algebra of the free Lie algebra generated by the fundamental representation of the symplectic group. It gives an alternative proof of the fact first shown by Bartholdi that the top rational homology group of the moduli space of metric graphs of rank 7 is one dimensional. As an application, we construct a non-trivial abelian quotient of the homology cobordism group of a surface of positive genus. This talk is based on joint works with Shigeyuki Morita, Masaaki Suzuki and Gwénaël Massuyeau.
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