Seminar information archive

Seminar information archive ~05/21Today's seminar 05/22 | Future seminars 05/23~

2014/01/09

FMSP Lectures

14:50-16:20   Room #056 (Graduate School of Math. Sci. Bldg.)
Rinat Kashaev (University of Geneva)
Lectures on quantum Teichmüller theory I (ENGLISH)
[ Abstract ]
Quantum Teichmüller theory leads to a family of unitary infinite dimensional projective representations of the mapping class groups of punctured surfaces. One of the recent applications of this theory is the construction of state integral three-manifold invariants related with hyperbolic geometry.
In these lectures it is planned to address the following subjects:
1) Penner’s coordinates in the decorated Teichmüller space.
2) Ratio coordinates.
3) Quantization.
4) The length spectrum of simple closed curves.
[ Reference URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Kashaev.pdf

2014/01/08

Operator Algebra Seminars

16:30-18:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Sakae Fuchino (Kobe University)
Dow's metrization theorem and beyond (JAPANESE)

Number Theory Seminar

16:40-17:40   Room #056 (Graduate School of Math. Sci. Bldg.)
Sho Yoshikawa (University of Tokyo)
Roots of the discriminant of an elliptic curves and its torsion points (JAPANESE)
[ Abstract ]
We give an explicit and intrinsic description of (the torsor defined by the 12th roots of) the discriminant of an elliptic curve using the group of its 12-torsion points and the Weil pairing. As an application, we extend a result of Coates (which deals with the characteristic 0 case) to the case where the characteristic of the base field is not 2 or 3. This is a joint work with Kohei Fukuda.

2013/12/26

Operator Algebra Seminars

16:30-18:00   Room #118 (Graduate School of Math. Sci. Bldg.)
Shuhei Masumoto (Univ. Tokyo)
Countable Chain Condition for $C^*$-algebras (ENGLISH)

2013/12/25

GCOE Seminars

16:00-17:00   Room #270 (Graduate School of Math. Sci. Bldg.)
Kazufumi Ito (North Carolina State University)
Nonsmooth Nonconvex Optimization Problems (ENGLISH)
[ Abstract ]
A general class of nonsmooth nonconvex optimization problems is discussed. A general existence theory of solutions, the Lagrange multiplier theory and sensitivity analysis of the optimal value function are developed. Concrete examples are presented to demonstrate the applicability of our approach.

2013/12/24

Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Tirasan Khandhawit (Kavli IPMU)
Stable homotopy type for monopole Floer homology (ENGLISH)
[ Abstract ]
In this talk, I will try to give an overview of the
construction of stable homotopy type for monopole Floer homology. The
construction associates a stable homotopy object to 3-manifolds, which
will recover the Floer groups by appropriate homology theory. The main
ingredients are finite dimensional approximation technique and Conley
index theory. In addition, I will demonstrate construction for certain
3-manifolds such as the 3-torus.

2013/12/20

GCOE Seminars

15:00-16:00   Room #118 (Graduate School of Math. Sci. Bldg.)
Mourad Bellassoued (Bizerte University)
Determination of the magnetic field in an anisotropic Schrodinger equation (ENGLISH)
[ Abstract ]
This talk is devoted to the study of the following inverse boundary value problem: given a Riemannian manifold with boundary, determine the magnetic potential in a dynamical Schroedinger equation in a magnetic field from the observations made at the boundary.

2013/12/19

Lectures

17:00-18:00   Room #270 (Graduate School of Math. Sci. Bldg.)
Guanghui Hu (WIAS, Germany)
Inverse elastic wave scattering from rigid diffraction gratings (ENGLISH)
[ Abstract ]
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.

FMSP Lectures

17:00-18:00   Room #270 (Graduate School of Math. Sci. Bldg.)
Guanghui Hu (WIAS, Germany)
Inverse elastic wave scattering from rigid diffraction gratings (ENGLISH)
[ Abstract ]
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.
[ Reference URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Hu.pdf

2013/12/18

Number Theory Seminar

18:00-19:00   Room #117 (Graduate School of Math. Sci. Bldg.)
Kazuya Kato (University of Chicago)
Heights of motives (ENGLISH)
[ Abstract ]
The height of a rational number a/b (a, b integers which are coprime) is defined as max(|a|, |b|). A rational number with small (resp. big) height is a simple (resp. complicated)  number. Though the notion height is so naive, height has played fundamental roles in number theory. There are important variants of this notion. In 1983, when Faltings proved Mordell conjecture, Faltings first proved Tate conjecture for abelian variaties by defining heights of abelian varieties, and then he deduced Mordell conjecture from the latter conjecture. I explain that his height of an abelian variety is generalized to the height of a motive. This generalization of height is related to open problems in number theory. If we can prove finiteness of the number of motives of bounded heights, we can prove important conjectures in number theory such as general Tate conjecture and Mordell-Weil type conjectures in many cases.

2013/12/17

Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Inasa Nakamura (The University of Tokyo)
Satellites of an oriented surface link and their local moves (JAPANESE)
[ Abstract ]
For an oriented surface link $F$ in $\\mathbb{R}^4$,
we consider a satellite construction of a surface link, called a
2-dimensional braid over $F$, which is in the form of a covering over
$F$. We introduce the notion of an $m$-chart on a surface diagram
$p(F)\\subset \\mathbb{R}^3$ of $F$, which is a finite graph on $p(F)$
satisfying certain conditions and is an extended notion of an
$m$-chart on a 2-disk presenting a surface braid.
A 2-dimensional braid over $F$ is presented by an $m$-chart on $p(F)$.
It is known that two surface links are equivalent if and only if their
surface diagrams are related by a finite sequence of ambient isotopies
of $\\mathbb{R}^3$ and local moves called Roseman moves.
We show that Roseman moves for surface diagrams with $m$-charts can be
well-defined. Further, we give some applications.

Tuesday Seminar of Analysis

16:30-18:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Fabricio Macia (Universidad Politécnica de Madrid)
Dispersion and observability for completely integrable Schrödinger flows (ENGLISH)
[ Abstract ]
I will present some results on weak dispersion and unique continuation (observability) for linear Schrödinger
equations that are obtained as the quantization of a completely integrable Hamiltonian system.
The model case corresponds to the linear Schrödinger equation (with a potential) on the flat torus.
Our results are obtained through a detailed analysis of semiclassical measures corresponding to
sequences of solutions, which is performed using a two-microlocal approach.
This is a joint work with Nalini Anantharaman and Clotilde Fermanian-Kammerer.

Lie Groups and Representation Theory

16:30-17:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Koichi Kaizuka (University of Tsukuba)
A characterization of the $L^{2}$-range of the
Poisson transform on symmetric spaces of noncompact type (JAPANESE)
[ Abstract ]
Characterizations of the joint eigenspaces of invariant
differential operators in terms of the Poisson transform have been one of the central problems in harmonic analysis on symmetric spaces.
From the point of view of spectral theory, Strichartz (J. Funct.
Anal.(1989)) formulated a conjecture concerning a certain image
characterization of the Poisson transform of the $L^{2}$-space on the boundary on symmetric spaces of noncompact type. In this talk, we employ techniques in scattering theory to present a positive answer to the Strichartz conjecture.

2013/12/16

FMSP Lectures

15:30-16:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Jon Nimmo (Univ. of Glasgow)
The discrete Schrodinger equation for compact support potentials (ENGLISH)
[ Abstract ]
We consider the exact form of the Jost solutions of the discrete Schrodinger equation for arbitrary potentials with compact support. Remarkably, these solutions may be written in terms of certain explicitly defined polynomials in the non-trivial values of the potential. These polynomials also arise in the work of Yamada (2000) in connection with a birational representation of the symmetric group.
Applications of this approach to the udKdV are also discussed.
[ Reference URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_%20NIMMO.pdf

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Yusaku Tiba (Tokyo Institute of Technology)
Shilov boundaries of the pluricomplex Green function's level sets (JAPANESE)
[ Abstract ]
In this talk, we study a relation between the Shilov boundaries of the pluricomplex Green function's level sets and supports of Monge-Ampére type currents.

2013/12/12

Applied Analysis

16:00-17:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Yuki Yasuda (University of Tokyo (Department of Earth and Planetary Science))
A theoretical study on the spontaneous radiation of atmospheric gravity waves using the renormalization group method (JAPANESE)

2013/12/10

FMSP Lectures

13:00-14:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Erwin Bolthausen (University of Zurich)
Random walks in random environments (ENGLISH)
[ Reference URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Bolthausen.pdf

Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Motoo Tange (University of Tsukuba)
Corks, plugs, and local moves of 4-manifolds. (JAPANESE)
[ Abstract ]
Akbulut and Yasui defined cork, and plug
to produce many exotic pairs.
In this talk, we introduce a plug
with respect to Fintushel-Stern's knot surgery
or more 4-dimensional local moves and
and argue by using Heegaard Fleor theory.

Tuesday Seminar of Analysis

16:30-18:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Abel Klein (UC Irvine)
Quantitative unique continuation principle, local behavior of solutions, and bounds on the density of states for Schr\\"odinger operators (ENGLISH)
[ Abstract ]
We establish bounds on the density of states measure for Schr\\"odinger operators. These are deterministic results that do not require the existence of the density of states measure, or, equivalently, of the integrated density of states. The results are stated in terms of a ``density of states outer-measure'' that always exists, and provides an upper bound for the density of states measure when it exists. We prove log-H\\"older continuity for this density of states outer-measure in one, two, and three dimensions for Schr\\"odinger operators, and in any dimension for discrete Schr\\"odinger operators. Our proofs use a quantitative unique continuation principle and the local behavior of approximate solutions of the stationary Schr\\"odinger equation.
(Joint work with Jean Bourgain.)
References: Jean Bourgain and Abel Klein: Bounds on the density of states for Schr\\"odinger operators. Invent. Math. 194, 41-72 (2013).

2013/12/09

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Toshiki Mabuchi (Osaka University)
Donaldson-Tian-Yau 予想と K-安定性について (JAPANESE)

Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Takuzo Okada (Saga University)
On birationally tririgid Q-Fano threefolds (JAPANESE)
[ Abstract ]
I will talk about birational geometry of Q-Fano threefolds. A Mori
fiber space birational to a given Q-Fano threefold is called a birational Mori fiber structure of the threefold. The existence of Q-Fano threefolds with a unique birational Mori fiber structure (resp. with two birational Mori fiber structures) is known. In this talk I will give an example of Q-Fano threefolds with three birational Mori fiber structures and also discuss about the behavior of birational Mori fiber structures in a family.

2013/12/06

Geometry Colloquium

17:00-18:00   Room #123 (Graduate School of Math. Sci. Bldg.)
Sadayoshi KOJIMA (Tokyo Institute of Technology)
Normalized entropy versus volume for pseudo-Anosovs (JAPANESE)
[ Abstract ]
We establish an explicit linear inequality between the normalized entropy of pseudo-Anosov automorphisms and the hyperbolic volume of their mapping tori, based on a recent result by Jean-Marc Schlenker on renormalized volume of quasi-Fuchsian
manifolds. This is a joint work with Greg McShane.

FMSP Lectures

16:30-18:00   Room #118 (Graduate School of Math. Sci. Bldg.)
Simon Gindikin (Rutgers University)
Horospheres: geometry and analysis (II) (ENGLISH)
[ Abstract ]
About 50 years ago Gelfand suggested a concepion of horospherical transform which, he hoped, must be an universal principle unifying non commutative harmonic analysis. I want to make several historic remarks (especialy, since this year is the centenial anniversary of Gelfand). I want to discuss the evolution of this fundamental conception for 50 years and how Gelfand’s dreams are looked today. I will discuss an elementary case of hyperboloids of any signature where there were not too much progress after old initial result of Gelfand-Graev.
[ Reference URL ]
http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_Gindikin.pdf

Colloquium

16:30-17:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Naoki Imai (Graduate School of Mathematical Scinences, The University of Tokyo)
Local Langlands correspondence and Lubin-Tate perfectoid spaces (JAPANESE)

Colloquium

16:30-17:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Naoki Imai (Graduate School of Mathematical Sciences, The University of Tokyo)
Local Langlands correspondence and Lubin-Tate perfectoid spaces (JAPANESE)

< Previous 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135 Next >