Seminar information archive

Seminar information archive ~02/21Today's seminar 02/22 | Future seminars 02/23~

Tuesday Seminar of Analysis

16:30-18:00   Room #118 (Graduate School of Math. Sci. Bldg.)
Tom\'as Lungenstrass (Pontificia Universidad Catolica de Chile)
A Trace Formula for Long-Range Perturbations of the Landau Hamiltonian
(Joint work with Georgi Raikov) (ENGLISH)
[ Abstract ]
The Landau Hamiltonian describes the dynamics of a two-dimensional
charged particle subject to a constant magnetic field. Its spectrum
consists in eigenvalues of infinite multiplicity given by $B(2q+1)$, $q\\in Z_+$. We
consider perturbations of this operator by including a continuous
electric potential that decays slowly at infinity (as $|x|^{-\\rho}$, $0<\\rho<1$).
The spectrum of the perturbed operator consists of eigenvalue clusters
which accumulate to the Landau levels. We provide estimates for the
rate at which the clusters shrink as we move up the energy levels.
Further, we obtain an explicit description of the asymptotic density
of eigenvalues for asymptotically homogeneous long-range potentials in
terms of a mean-value transform of the associated homogeneous
function.

2013/07/08

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Hisashi Kasuya (Tokyo Institute of Technology)
Cohomologies and deformations of solvmanifolds (JAPANESE)
[ Abstract ]
$G$を単連結可解リー群とし, $G$はココンパクト離散部分群$\Gamma$を持つとする. この時, コンパクト等質空間$G/\Gamma$をsolvmanifoldと呼ぶ. 本講演では, solvmanifoldのde Rhamコホモロジー, Dolbeaultコホモロジー, Bott-Chernコホモロジーの計算法を紹介する. さらにその計算法を用いた, ホッジ理論と変形理論の研究を紹介する.

Kavli IPMU Komaba Seminar

17:00-18:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Richard Eager (Kavli IPMU)
Elliptic genera and two dimensional gauge theories (ENGLISH)
[ Abstract ]
The elliptic genus is an important invariant of two dimensional conformal field theories that generalizes the Witten index. In this talk, I will first review the geometric meaning of the elliptic genus and Witten's GLSM construction. Then I will explain how the elliptic genus can be computed directly from a two dimensional gauge theory using localization. The central example of this talk will be the quintic threefold. The GLSM description of the quintic threefold has both a large-volume sigma model description and a Landau-Ginzburg description. I will explain how the GLSM calculation of the index reproduces the old results in these two phases. Time permitting, further applications and generalizations will be discussed.

Lectures

10:40-12:10   Room #128 (Graduate School of Math. Sci. Bldg.)
Hirofumi Izuhara (Meiji Institute for Advanced Study of Mathematical Sciences,
Meiji University)
Aggregation mechanism of biological species : from microscopic
and macroscopic viewpoints (JAPANESE)
[ Abstract ]
There are a lot of organisms which form aggregation in nature. In order to describe the dynamics of such biological species, a particle model is often proposed, which is based on the random walk from the microscopic point of view. On the other hand, when we take population densities of biological species into account, the dynamics is expressed as partial differential equations. We see that different models are proposed according to the viewpoints which we are focusing on. In this talk, we take aggregation phenomena of biological species as an example, and introduce a relation between a microscopic particle model and a macroscopic partial differential equation model.

FMSP Lectures

16:15-17:15   Room #270 (Graduate School of Math. Sci. Bldg.)
Oleg Emanouilov (Colorado State Univ.)
Two-dimensional Calderon problems for Navier-Stokes equations and Lame system (ENGLISH)
[ Abstract ]
We will prove the uniqueness in determining viscosity in two-dimensional Navier-Stokes equations by Dirichlet-to-Neumann map.
Moreover, without any smallness assumption, we establish the uniqueness in determining two Lame coefficients in two-dimensional isotropic Lame system Dirichlet-to-Neumann map.

2013/07/05

FMSP Lectures

16:30-18:00   Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (IV) Applications to differential geometry and foliations (ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf

2013/07/04

Seminar on Probability and Statistics

14:50-16:00   Room #052 (Graduate School of Math. Sci. Bldg.)
SUZUKI, Taiji (Tokyo Institute of Technology)
低ランク行列推定におけるベイズ推定法の性質 (JAPANESE)
[ Abstract ]
真のパラメータが低ランク行列の構造を持つような低ランク行列推定問題を考える. 低ランク行列推定問題の例としては,低ランク行列の一部が見えている時にその残りを 推定する行列補完の問題などがある.応用としてはユーザへの推薦システムなどがある. これまでの理論解析は主にスパース正則化を用いた経験誤差最小化を対象としてきたが, 本発表ではベイズ法を考え,その統計的性質を調べる.ベイズ法においては, 正則化付き経験誤差最小化による方法とは異なるやや緩い仮定のもと, ほぼ最適な収束レートが導けることを示す.また,テンソル型データ (多次元アレイデータ)へも同様の議論が拡張可能であることも述べる.
[ Reference URL ]
http://www.sigmath.es.osaka-u.ac.jp/~kamatani/statseminar/2013/02.html

2013/07/03

Number Theory Seminar

16:40-17:40   Room #056 (Graduate School of Math. Sci. Bldg.)
Takehito Yoshiki (University of Tokyo)
A general formula for the discriminant of polynomials over $¥mathbb{F}_2$ determining the parity of the number of prime factors
(JAPANESE)
[ Abstract ]
In order to find irreducible polynomials over $\\mathbb{F}_2$ efficiently, the method using Swan's theorem is known. Swan's theorem determines the parity of the numberof irreducible factors of a polynomial $f$ over $\\mathbb{F}_2$ with no repeated root, by using the discriminant ${\\rm D}(\\tilde{f})\\pmod 8$, where $\\tilde{f}$ is a monic polynomial over $\\mathbb{Z}_2$ such that $\\tilde{f}=f\\pmod 2$. In the lecture, we will give the formula for the discriminant ${\\rm D}(\\tilde{f}) \\pmod 8$ for a polynomial $f$ over $\\mathbb{F}_2$ with no repeated root. By applying this formula to various types of polynomials, we shall get the parity of the number of irreducible factors of them.

2013/07/02

Numerical Analysis Seminar

16:30-18:00   Room #002 (Graduate School of Math. Sci. Bldg.)
Masaru Miyashita (Sumitomo Heavy Industries, Ltd.)
Numerical plasma simulation for reactive plasma deposition (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/

2013/06/29

Harmonic Analysis Komaba Seminar

13:00-18:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Yoshihiro Sawano (Tokyo Metropolitan University) 13:30-15:00
Critical Sobolev embedding of function spaces and the real interpolation functor
(JAPANESE)
[ Abstract ]
We consider the endpoint case of the Sobolev embedding.
It is well known that the function spaces such as Sobolev spaces are not embedded into L^¥infty in the critical case.
One of the remedies is the Brezis-Gallouet-Wainger type
estimate. However, such an estimate involve the log term
and it can not be regarded as the norm.
In this talk, by using the real interpolation functor, we propose another formulation. We compare
the existing result with our new results.
If time permits, we mention some related results.
Mai Fujita (Osaka University) 15:30-17:00
On weighted estimates for multilinear Fourier multipliers with Sobolev regularity
(JAPANESE)

2013/06/28

FMSP Lectures

16:00-17:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Yoichiro Mori (University of Minnesota)
Mathematical model for the electrodiffusion of ions, Lecture II (JAPANESE)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~fmsp/files/FMSPLectures_Mori.pdf

Colloquium

16:30-17:30   Room #123 (Graduate School of Math. Sci. Bldg.)
Hiroki Kodama (Graduate School of Mathematical Sciences, The University of Tokyo)
The Geometry of protain modelling (JAPANESE)

2013/06/27

FMSP Lectures

16:30-18:00   Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (III) Curvature of metric measure spaces II
(ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf

Geometry Colloquium

10:00-11:30   Room #122 (Graduate School of Math. Sci. Bldg.)
MASAI, Hidetoshi (Tokyo Institute of Technology)
On volume formulae in terms of orthospectrum (JAPANESE)
[ Abstract ]
Bridgeman-Kahn and Calegari derived formulae to compute the volumes of compact hyperbolic n-manifolds with totally geodesic boundary in terms of orthospectrum. Here the orthospectrum is the set of length of geodesics perpendicular to the boundary at both ends. The two formulae are obtained by apparently different methods. In this talk, we prove that the two volume formulae coincide. We also discuss some interesting relationship between two formulae. This work is a joint work with Greg McShane.

FMSP Lectures

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)
Yoichiro Mori (University of Minnesota)
Mathematical model for the electrodiffusion of ions, Lecture I (JAPANESE)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~fmsp/files/FMSPLectures_Mori.pdf

2013/06/26

Number Theory Seminar

16:40-17:40   Room #056 (Graduate School of Math. Sci. Bldg.)
Kousuke Suzuki (University of Tokyo)
An explicit construction of point sets with large minimum Dick weight (JAPANESE)
[ Abstract ]
Walsh figure of merit WAFOM($P$) is a quality measure of point sets $P$ for quasi-Monte Carlo integration constructed by a digital net method. WAFOM($P$) is bounded by the minimum Dick weight of $P^¥perp$, where the Dick weight is a generalization of Hamming weight. In this talk, we give an explicit construction of point sets with large minimum Dick weight using Niederreiter-Xing sequences and Dick's interleaving construction. These point sets are also examples of low-WAFOM point sets.

2013/06/25

Tuesday Seminar on Topology

17:10-18:10   Room #056 (Graduate School of Math. Sci. Bldg.)
Tadayuki Watanabe (Shimane University)
Higher-order generalization of Fukaya's Morse homotopy
invariant of 3-manifolds (JAPANESE)
[ Abstract ]
In his article published in 1996, K. Fukaya constructed
a 3-manifold invariant by using Morse homotopy theory. Roughly, his
invariant is defined by considering several Morse functions on a
3-manifold and counting with weights the ways that the theta-graph can
be immersed such that edges follow gradient lines. We generalize his
construction to 3-valent graphs with arbitrary number of loops for
integral homology 3-spheres. I will also discuss extension of our method
to 3-manifolds with positive first Betti numbers.

Numerical Analysis Seminar

16:30-18:00   Room #002 (Graduate School of Math. Sci. Bldg.)
Teruya Minamoto (Saga University)
Digital watermarking methods using the wavelet transforms and interval arithmetic (JAPANESE)
[ Reference URL ]
http://www.infsup.jp/utnas/

2013/06/22

Monthly Seminar on Arithmetic of Automorphic Forms

10:00-12:15   Room #123 (Graduate School of Math. Sci. Bldg.)
*** (***) 10:00-11:00
*** (JAPANESE)
*** (***) 11:15-12:15
*** (JAPANESE)

Monthly Seminar on Arithmetic of Automorphic Forms

10:00-12:15   Room #123 (Graduate School of Math. Sci. Bldg.)
Kei-ichi Gunji (Chiba Inst. Tech) 10:00-11:00
On the computation of the ramified Siegel series associated with
trivial character (JAPANESE)
[ Abstract ]
Please check the Japanese version of the web page.
Masao Tsuzuki (Sophia University) 11:15-12:15
An explicit relative trace formula for Hilbert modular forms and its applications
(JAPANESE)
[ Abstract ]
This is joint work with Shingo Sugiyama. In this talk, we report our recent result on relative trace formula on PGL(2) computing the spectral averages for the central L-values of quadratic base change of holomorphic Hilbert mudular forms. explicitly all local terms of the trace formula, dropping several assumptions which have always been assumed in existing works of similar theme. The following applications of our explicit relative trace formula will be explained:
(i) a spectral equidistribution result in the leve aspect for the Satake parameters weighted by central L-values;
(ii) a subconvexity bound of quadratic base change L-functions for holomorphic Hilbert cusp forms in the weight aspect;
(iii) Existence of infinitely many holomorphic Hilbert cusp forms with arbitrarily large field of definition and with non vanishing central $L$-values.

2013/06/20

FMSP Lectures

16:30-18:00   Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (II) Curvature of metric measure spaces I (ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf

2013/06/19

Number Theory Seminar

16:40-17:40   Room #056 (Graduate School of Math. Sci. Bldg.)
Wataru Kai (University of Tokyo)
A p-adic exponential map for the Picard group and its application to curves (JAPANESE)
[ Abstract ]
Let $\\mathcal{X}$ be a proper flat scheme over a complete discrete valuation ring $O_k$ of characteristic $(0,p)$. We define an exponential map from a subgroup of the first cohomology group of $O_¥mathcal{X}$ to the Picard group of $\\mathcal{X}$, mimicking the classical construction in complex geometry. This exponential map can be applied to prove a surjectivity property concerning the Albanese variety $Alb_{X}$ of a smooth variety $X$ over $k$.

FMSP Lectures

14:40-16:10   Room #002 (Graduate School of Math. Sci. Bldg.)
Szymon M. Walczak (University of Lodz, Poland)
Geometric applications of Wasserstein distance,
Lecture (I) Wasserstein distance and optimal transportation
(ENGLISH)
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/~topology/Walczak.pdf

Operator Algebra Seminars

16:30-18:00   Room #118 (Graduate School of Math. Sci. Bldg.)
Yosuke Kubota (Univ. Tokyo)
A generalization of the spectral flow and localization of index (ENGLISH)

2013/06/18

Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Kimihiko Motegi (Nihon University)
Left-orderable, non-L-space surgeries on knots (JAPANESE)
[ Abstract ]
A Dehn surgery is said to be left-orderable
if the resulting manifold of the surgery has the left-orderable fundamental group,
and a Dehn surgery is called an L-space surgery
if the resulting manifold of the surgery is an L-space.
We will focus on left-orderable, non-L-space surgeries on knots in the 3-sphere.
Once we have a knot with left-orderable surgeries,
the ``periodic construction" enables us to provide infinitely many knots with
left-orderable, non-L-space surgeries.
We apply the construction to present infinitely many hyperbolic knots on each
of which every nontrivial surgery is a left-orderable, non-L-space surgery.
This is a joint work with Masakazu Teragaito.

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