Seminar information archive

Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Alexandru Dimca (Institut Universitaire de France )
Syzygies of jacobian ideals and Torelli properties (ENGLISH)
[ Abstract ]
Let $C$ be a reduced complex projective plane curve defined by a homogeneous equation $f(x,y,z)=0$. We consider syzygies of the type $af_x+bf_y+cf_z=0$, where $a,b,c$ are homogeneous polynomials and $f_x,f_y,f_z$ stand for the partial derivatives of $f$. In our talk we relate such syzygies with stable or splittable rank two vector bundles on the projective plane, and to Torelli properties of plane curves in the sense of Dolgachev-Kapranov.

2014/04/26

Monthly Seminar on Arithmetic of Automorphic Forms

13:30-16:00   Room #123 (Graduate School of Math. Sci. Bldg.)
Ryutarou Okazaki (Doushisha Univ. until March, 2014) 13:30-14:30
The estimate of integral points of F(X,Y)=1, with F being a integral homogeneous quartic form F of degree 4 (JAPANESE)
Ryutarou Okazaki (Doushisha Univ. until March, 2014) 15:00-16:00
Moduli of teh pairs of algebraic curve of genus 2 and its unramified cover of degree 7 (joint work with Hoffmann) (JAPANESE)

2014/04/24

Geometry Colloquium

10:00-11:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Hiraku Nozawa (Ritsumeikan University)
On rigidity of Lie foliations (JAPANESE)
[ Abstract ]
If the leaves of a Lie foliation are isometric to a symmetric space of noncompact type of higher rank, then, by a theorem of Zimmer, the holonomy group of the Lie foliation has rigidity similar to that of lattices of semisimple Lie groups of higher rank. The main result of this talk is a generalization of Zimmer's theorem including the case of real rank one based on an application of a variant of Mostow rigidity. (This talk is based on a joint work with Ga¥"el Meigniez.)

2014/04/23

Operator Algebra Seminars

16:30-18:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Takuya Takeishi (Univ. Tokyo)
Bost-Connes system for local fields of characteristic zero (ENGLISH)

Number Theory Seminar

16:40-17:40   Room #002 (Graduate School of Math. Sci. Bldg.)
Yoichi Mieda (University of Tokyo)
Non-tempered A-packets and the Rapoport-Zink spaces (JAPANESE)

Mathematical Biology Seminar

14:50-16:20   Room #128 (Graduate School of Math. Sci. Bldg.)
Yukihiko Nakata (Graduate School of Mathematical Sciences, University of Tokyo)
Age-structured epidemic model with infection during transportation (JAPANESE)

2014/04/22

Tuesday Seminar of Analysis

16:30-18:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Yohei Tsutsui (The University of Tokyo)
Bounded small solutions to a chemotaxis system with
non-diffusive chemical (JAPANESE)
[ Abstract ]
We consider a chemotaxis system with a logarithmic
sensitivity and a non-diffusive chemical substance. For some chemotactic
sensitivity constants, Ahn and Kang proved the existence of bounded
global solutions to the system. An entropy functional was used in their
argument to control the cell density by the density of the chemical
substance. Our purpose is to show the existence of bounded global
solutions for all the chemotactic sensitivity constants. Assuming the
smallness on the initial data in some sense, we can get uniform
estimates for time. These estimates are used to extend local solutions.
This talk is partially based on joint work with Yoshie Sugiyama (Kyusyu
Univ.) and Juan J. L. Vel\\'azquez (Univ. of Bonn).

2014/04/21

Numerical Analysis Seminar

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Takashi Nakazawa (Tohoku University)
Shape optimization problems for time-periodic solutions of the Navier-Stokes equations (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Hikaru Yamamoto (The University of Tokyo)
Lagrangian mean curvature flows and some examples (JAPANESE)

2014/04/19

Harmonic Analysis Komaba Seminar

13:30-17:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Strichartz estimates for incompressible rotating fluids (JAPANESE)
Masami Okada (Tokyo Metropolitan Unversity) 15:30-16:30
On the interpolation of functions for scattered data on random infinite points with a sharp error estimate (JAPANESE)

2014/04/16

Number Theory Seminar

17:30-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Olivier Wittenberg (ENS and CNRS)
On the cycle class map for zero-cycles over local fields (ENGLISH)
[ Abstract ]
The Chow group of zero-cycles of a smooth and projective variety defined over a field k is an invariant of an arithmetic and geometric nature which is well understood only when k is a finite field (by higher-dimensional class field theory). In this talk, we will discuss the case of local and strictly local fields. We prove in particular the injectivity of the cycle class map to integral l-adic cohomology for a large class of surfaces with positive geometric genus over p-adic fields. The same statement holds for semistable K3 surfaces over C((t)), but does not hold in general for surfaces over C((t)) or over the maximal unramified extension of a p-adic field. This is a joint work with Hélène Esnault.

2014/04/15

Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Takahito Naito (The University of Tokyo)
On the rational string operations of classifying spaces and the
Hochschild cohomology (JAPANESE)
[ Abstract ]
Chataur and Menichi initiated the theory of string topology of
classifying spaces.
In particular, the cohomology of the free loop space of a classifying
space is endowed with a product
called the dual loop coproduct. In this talk, I will discuss the
algebraic structure and relate the rational dual loop coproduct to the
cup product on the Hochschild cohomology via the Van den Bergh isomorphism.

PDE Real Analysis Seminar

10:30-11:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Yohei Tsutsui (The University of Tokyo)
An application of weighted Hardy spaces to the Navier-Stokes equations (JAPANESE)
[ Abstract ]
The purpose of this talk is to investigate decay orders of the L^2 energy of solutions to the incompressible homogeneous Navier-Stokes equations on the whole spaces by the aid of the theory of weighted Hardy spaces. The main estimates are two weighted inequalities for heat semigroup on weighted Hardy spaces and a weighted version of the div-curl lemma due to Coifman-Lions-Meyer-Semmes. It turns out that because of the use of weighted Hardy spaces, our decay orders of the energy can be close to the critical one of Wiegner.

Lie Groups and Representation Theory

16:30-18:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Shunsuke Tsuchioka (the University of Tokyo)
Toward the graded Cartan invariants of the symmetric groups (JAPANESE)
[ Abstract ]
We propose a graded analog of Hill's conjecture which is equivalent to K\\"ulshammer-Olsson-Robinson's conjecture on the generalized Cartan invariants of the symmetric groups.
We give justifications for it and discuss implications between the variants.
Some materials are based on the joint work with Anton Evseev.

2014/04/14

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Katsutoshi Yamanoi (Tokyo Institute of Technology)
Alternative proof of the geometric vrsion of Lemma on logarithmic derivatives (JAPANESE)

2014/04/10

Geometry Colloquium

10:00-11:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Kotaro Kawai ( University of Tokyo)
Deformations of homogeneous Cayley cone submanifolds (JAPANESE)
[ Abstract ]
A Cayley submanifold is a minimal submanifold in a Spin(7)-manifold, and is a special class of calibrated submanifolds introduced by Harvey and Lawson. The deformation of calibrated submanifolds is first studied by Mclean. He studied the compact case, and many people try to generalize it to noncompact cases (conical case, asymptotically conical case etc.). In general, the moduli space of deformations of a Cayley cone is known not to be smooth. In this talk, we focus on the homogeneous Cayley cones in R^8, and study their deformation spaces explicitly.

2014/04/09

Operator Algebra Seminars

16:30-18:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Ryszard Nest (Univ. Copenhagen)
Index and determnant of n-tuples of commuting operators (ENGLISH)

2014/04/08

Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Hidetoshi Masai (The University of Tokyo)
On the number of commensurable fibrations on a hyperbolic 3-manifold. (JAPANESE)
[ Abstract ]
By work of Thurston, it is known that if a hyperbolic fibred
$3$-manifold $M$ has Betti number greater than 1, then
$M$ admits infinitely many distinct fibrations.
For any fibration $\\omega$ on a hyperbolic $3$-manifold $M$,
the number of fibrations on $M$ that are commensurable in the sense of
Calegari-Sun-Wang to $\\omega$ is known to be finite.
In this talk, we prove that the number can be arbitrarily large.

Seminar on Probability and Statistics

13:00-14:10   Room #052 (Graduate School of Math. Sci. Bldg.)
Alexandre Brouste (Universite du Maine, France)
Parametric estimation in fractional Ornstein-Uhlenbeck process (ENGLISH)
[ Abstract ]
Several statistical models that imply the fractional Ornstein-Uhlenbeck (fOU) process will be presented: direct observations of the process or partial observations in an additive independent noise, continuous observations or discrete observations. In this different settings, we exhibit large sample (or high-frequency) asymptotic properties of the estimators (maximum likelihood estimator, quadratic variation based estimator, moment estimator, …) for all parameters of interest of the fOU. We also illustrate our results with the R package yuima.
[ Reference URL ]
http://www.sigmath.es.osaka-u.ac.jp/~kamatani/statseminar/2014/00.html

2014/03/19

Classical Analysis

16:00-17:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Anton Dzhamay (University of Northern Colorado)
Discrete Schlesinger Equations and Difference Painlevé Equations (ENGLISH)
[ Abstract ]
The theory of Schlesinger equations describing isomonodromic
dynamic on the space of matrix coefficients of a Fuchsian system
w.r.t.~continuous deformations is well-know. In this talk we consider
a discrete version of this theory. Discrete analogues of Schlesinger
deformations are Schlesinger transformations that shift the eigenvalues
of the coefficient matrices by integers. By discrete Schlesinger equations
we mean the evolution equations on the matrix coefficients describing
such transformations. We derive these equations, show how they can be
split into the evolution equations on the space of eigenvectors of the
coefficient matrices, and explain how to write the latter equations in
the discrete Hamiltonian form. We also consider some reductions of those
equations to the difference Painlevé equations, again in complete parallel
to the differential case.

This is a joint work with H. Sakai (the University of Tokyo) and
T.Takenawa (Tokyo Institute of Marine Science and Technology).

2014/03/14

GCOE Seminars

16:00-16:50   Room #118 (Graduate School of Math. Sci. Bldg.)
Kazufumi Ito (North Carolina State Univ.)
A new finite difference scheme based on staggered grids for Navier Stokes equations (ENGLISH)
[ Abstract ]
We develop a new method that uses the staggered grid only for the pressure node, i.e., the pressure gird is the center of the square cell and the velocities are at the node. The advantage of the proposed method compared to the standard staggered grid methods is that it is very straight forward to treat the boundary conditions for the velocity field, the fluid structure interaction, and to deal with the multiphase flow using the immersed interface methods. We present our analysis and numerical tests.

GCOE Seminars

17:00-17:50   Room #118 (Graduate School of Math. Sci. Bldg.)
Jun Zou (The Chinese University of Hong Kong)
Efficient Domain Decomposition Methods for a Class of Linear and Nonlinear Inverse Problems (ENGLISH)
[ Abstract ]
In this talk we shall present several new domain decomposition methods for solving some linear and nonlinear inverse problems. The motivations and derivations of the methods will be discussed, and numerical experiments will be demonstrated.

2014/03/13

Lectures

10:15-11:45   Room #470 (Graduate School of Math. Sci. Bldg.)
Michele Triestino (Ecole Normale Superieure de Lyon)
Almost sure triviality of the $C^1$-centralizer of random circle diffeomorphisms with periodic points (ENGLISH)
[ Abstract ]
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.

GCOE Seminars

17:00-18:00   Room #122 (Graduate School of Math. Sci. Bldg.)
STABILITY IN THE OBSTACLE PROBLEM FOR A SHALLOW SHELL (ENGLISH)
[ Reference URL ]
http://fmsp.ms.u-tokyo.ac.jp/bm02.pdf

2014/03/12

Lectures

10:15-11:45   Room #470 (Graduate School of Math. Sci. Bldg.)
Michele Triestino (Ecole Normale Superieure de Lyon)
Invariant distributions for circle diffeomorphisms of
irrational rotation number and low regularity (ENGLISH)
[ Abstract ]
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.