Seminar information archive

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Saotome Takanari
The Lyapunov-Schmidt reduction for the CR Yamabe equation on the Heisenberg group (Japanese)
[ Abstract ]
We will study CR Yamabe equation for a CR structure on the Heisenberg group which is deformed from the standard structure. By using Lyapunov-Schmidt reduction, it is shown that the perturbation of the standard CR Yamabe solution is a solution to the deformed CR Yamabe equation, under certain conditions of the deformation.

Tokyo Probability Seminar

16:50-18:20   Room #128 (Graduate School of Math. Sci. Bldg.)
Hiroshi Takahashi (College of Science and Technology, Nihon University)

Numerical Analysis Seminar

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Yuto Miyatake (Nagoya University)
Parallel energy-preserving methods for Hamiltonian systems (日本語)

2015/06/12

Geometry Colloquium

10:00-11:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Kota Hattori (Keio University)
The nonuniqueness of tangent cone at infinity of Ricci-flat manifolds (Japanese)
[ Abstract ]
For a complete Riemannian manifold (M,g), the Gromov-Hausdorff limit of (M, r^2g) as r to 0 is called the tangent cone at infinity. By the Gromov's Compactness Theorem, there exists tangent cone at infinity for every complete Riemannian manifolds with nonnegative Ricci curvatures. Moreover, if it is Ricci-flat, with Euclidean volume growth and having at least one tangent cone at infinity with a smooth cross section, then it is uniquely determined by the result of Colding and Minicozzi. In this talk I will explain that the assumption of the volume growth is essential for their uniqueness theorem.

2015/06/11

Applied Analysis

16:00-17:30   Room #128 (Graduate School of Math. Sci. Bldg.)

2015/06/10

Operator Algebra Seminars

16:45-18:15   Room #122 (Graduate School of Math. Sci. Bldg.)
David Kerr (Texas A&M Univ.)
Dynamics, dimension, and $C^*$-algebras

2015/06/09

Tuesday Seminar on Topology

17:00-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Manabu Akaho (Tokyo Metropolitan University)
Symplectic displacement energy for exact Lagrangian immersions (JAPANESE)
[ Abstract ]
We give an inequality of the displacement energy for exact Lagrangian
immersions and the symplectic area of punctured holomorphic discs. Our
approach is based on Floer homology for Lagrangian immersions and
Chekanov's homotopy technique of continuations. Moreover, we discuss our
inequality and the Hofer--Zehnder capacity.

2015/06/08

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Hisashi Kasuya (Tokyo Institute of Technology)
Mixed Hodge structures and Sullivan's minimal models of Sasakian manifolds (Japanese)
[ Abstract ]
By the result of Deligne, Griffiths, Morgan and Sullivan, the Malcev completion of the fundamental group of a compact Kahler manifold is quadratically presented. This fact gives good advances in "Kahler group problem" (Which groups can be the fundamental groups of compact Kahler manifolds?) In this talk, we consider the fundamental groups of compact Sasakian manifolds. We show that the Malcev Lie algebra of the fundamental group of a compact 2n+1-dimensional Sasakian manifold with n >= 2 admits a quadratic presentation by using Morgan's bigradings of Sullivan's minimal models of mixed-Hodge diagrams.

Tokyo Probability Seminar

16:50-18:20   Room #128 (Graduate School of Math. Sci. Bldg.)
Satoshi Yokoyama (Graduate School of Mathematical Sciences, The University of Tokyo)
On a stochastic Rayleigh-Plesset equation and a certain stochastic Navier-Stokes equation

2015/06/05

Geometry Colloquium

10:00-11:30   Room #126 (Graduate School of Math. Sci. Bldg.)
Yoshihiko Shinomiya (Shizuoka University)
Veech groups of Veech surfaces and periodic points
(日本語)
[ Abstract ]
Flat surfaces are surfaces with singular Euclidean structures.　The Veech group of a flat surface is the group consisting of all matrices inducing affine mappings of the flat surface. In this talk, we give relations between some geometrical values of flat surfaces and the signatures of Veech groups as Fuchsian groups. As an application of these relations, we estimate the numbers of periodic points of certain flat surfaces.

Seminar on Probability and Statistics

16:20-17:30   Room #056 (Graduate School of Math. Sci. Bldg.)

2015/06/03

Operator Algebra Seminars

16:45-18:15   Room #122 (Graduate School of Math. Sci. Bldg.)
Narutaka Ozawa (RIMS, Kyoto Univ.)
The Furstenberg boundary and $C^*$-simplicity

Mathematical Biology Seminar

14:55-16:40   Room #128演習室 (Graduate School of Math. Sci. Bldg.)
Shigehide Iwata (The graduate school of marine science and technology, Tokyo University of Marine Science and Technology)
Population dynamics of fish stock with migration and its management strategy

2015/06/01

Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Daizo Ishikawa (Waseda University)
Rank 2 weak Fano bundles on cubic 3-folds (日本語)
[ Abstract ]
A vector bundle on a projective variety is called weak Fano if its
projectivization is a weak Fano manifold. This is a　generalization of
Fano bundles.
In this talk, we will obtain a classification of rank 2 weak Fano
bundles on a nonsingular　cubic hypersurface in a projective 4-space.
Specifically, we will show that there exist rank 2 indecomposable weak
Fano bundles on it.

Tokyo Probability Seminar

16:50-18:20   Room #128 (Graduate School of Math. Sci. Bldg.)
Masato Hoshino (Graduate School of Mathematical Sciences, The University of Tokyo)

2015/05/28

Infinite Analysis Seminar Tokyo

17:00-18:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Yuki Arano (Graduate School of Mathematical Sciences, the University of Tokyo)
Unitary spherical representations of Drinfeld doubles (JAPANESE)
[ Abstract ]
It is known that the Drinfeld double of the quantized
enveloping algebra of a semisimple Lie algebra looks similar to the
quantized enveloping algebra of the complexification of the Lie algebra.
In this talk, we investigate the unitary representation theory of such
Drinfeld double via its analogy to that of the complex Lie group.
We also talk on an application to operator algebras.

2015/05/27

Operator Algebra Seminars

16:45-18:15   Room #122 (Graduate School of Math. Sci. Bldg.)
John F. R. Duncan (Case Western Reserve Univ.)
Vertex operator algebras in umbral Moonshine

Number Theory Seminar

17:00-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Ippei Nagamachi (University of Tokyo)
On a good reduction criterion for polycurves with sections (Japanese)

2015/05/26

Lie Groups and Representation Theory

17:00-18:30   Room #122 (Graduate School of Math. Sci. Bldg.)
Takeyoshi Kogiso (Josai University)
Local functional equations of Clifford quartic forms and homaloidal EKP-polynomials
[ Abstract ]
It is known that one can associate local functional equation to the irreducible relative invariant of an irreducible regular prehomogeneous vector spaces. We construct Clifford quartic forms that cannot obtained from prehomogeneous vector spaces, but, for which one can associate local functional equations. The characterization of polynomials which satisfy local functional equations is an interesting problem. In relation to this characterization problem (in a more general form), Etingof, Kazhdan and Polishchuk raised a conjecture. We make a counter example of this conjecture from Clifford quartic forms. (This is based on the joint work with F.Sato)

Tuesday Seminar on Topology

17:00-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Ken'ichi Kuga (Chiba University)
Introduction to formalization of topology using a proof assistant. (JAPANESE)
[ Abstract ]
Although the program of formalization goes back to David
Hilbert, it is only recently that we can actually formalize
substantial theorems in modern mathematics. It is made possible by the
development of certain type theory and a computer software called a
proof assistant. We begin this talk by showing our formalization of
some basic geometric topology using a proof assistant COQ. Then we
introduce homotopy type theory (HoTT) of Voevodsky et al., which
interprets type theory from abstract homotopy theoretic perspective.
HoTT proposes "univalent" foundation of mathematics which is
particularly suited for computer formalization.

2015/05/25

Seminar on Geometric Complex Analysis

10:30-12:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Tomoyuki Hisamoto (Nagoya Univ.)
On uniform K-stability (Japanese)
[ Abstract ]
It is a joint work with Sébastien Boucksom and Mattias Jonsson. We first introduce functionals on the space of test configurations, as non-Archimedean analogues of classical functionals on the space of Kähler metrics. Then, uniform K-stability is defined as a counterpart of K-energy's coercivity condition. Finally, reproving and strengthening Y. Odaka's results, we study uniform K-stability of Kähler-Einstein manifolds.

Algebraic Geometry Seminar

15:30-17:00   Room #122 (Graduate School of Math. Sci. Bldg.)
Yuya Matsumoto (University of Tokyo)
Good reduction of K3 surfaces (日本語 or English)
[ Abstract ]
We consider degeneration of K3 surfaces over a 1-dimensional base scheme
of mixed characteristic (e.g. Spec of the p-adic integers).
Under the assumption of potential semistable reduction, we first prove
that a trivial monodromy action on the l-adic etale cohomology group
implies potential good reduction, where potential means that we allow a
finite base extension.
Moreover we show that a finite etale base change suffices.
The proof for the first part involves a mixed characteristic
3-dimensional MMP (Kawamata) and the classification of semistable
degeneration of K3 surfaces (Kulikov, Persson--Pinkham, Nakkajima).
For the second part, we consider flops and descent arguments. This is a joint work with Christian Liedtke.
[ Reference URL ]
http://www.ms.u-tokyo.ac.jp/~ymatsu/index_j.html

Tokyo Probability Seminar

16:50-18:20   Room #128 (Graduate School of Math. Sci. Bldg.)
Yu Kitabeppu (Graduate School of Sciences, Kyoto University)
A finite diameter theorem on RCD spaces

2015/05/21

Lectures

16:00-17:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Gunnar Carlsson (Stanford University, Ayasdi INC)
The Shape of Data
(ENGLISH)
[ Abstract ]
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.
[ Reference URL ]
http://faculty.ms.u-tokyo.ac.jp/Carlsson.html

2015/05/20

Number Theory Seminar

17:30-18:30   Room #056 (Graduate School of Math. Sci. Bldg.)
Shou-Wu Zhang (Princeton University)
Colmez' conjecture in average (English)
[ Abstract ]
This is a report on a joint work with Xinyi Yuan on a conjectured formula of Colmez about the Faltings heights of CM abelian varieties. I will sketch a deduction of this formula in average of CM types from our early work on Gross-Zagier formula. When combined with a recent work of Tsimerman, this result implies the Andre-Oort conjecture for the moduli of abelian varieties.
Our method is different than a recently announced proof of a weaker form of the average formula by Andreatta, Howard, Goren, and Madapusi Pera: we use neither high dimensional Shimura varieties nor Borcherds' liftings.