## Seminar information archive

Seminar information archive ～02/15｜Today's seminar 02/16 | Future seminars 02/17～

### 2018/02/01

#### thesis presentations

9:15-10:30 Room #122 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

10:45-12:00 Room #122 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

10:45-12:00 Room #126 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

12:45-14:00 Room #118 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

12:45-14:00 Room #122 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

14:15-15:30 Room #118 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

14:15-15:30 Room #122 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

14:15-15:30 Room #126 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

15:45-17:00 Room #118 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

15:45-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

15:45-17:00 Room #126 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

17:15-18:30 Room #118 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

17:15-18:30 Room #122 (Graduate School of Math. Sci. Bldg.)

#### thesis presentations

17:15-18:30 Room #126 (Graduate School of Math. Sci. Bldg.)

### 2018/01/30

#### Tuesday Seminar on Topology

17:00-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Persistence-like distance on Tamarkin's category and symplectic displacement energy (JAPANESE)

**Yuichi Ike**(The University of Tokyo)Persistence-like distance on Tamarkin's category and symplectic displacement energy (JAPANESE)

[ Abstract ]

The microlocal sheaf theory due to Kashiwara and Schapira can be regarded as Morse theory with sheaf coefficients. Recently it has been applied to symplectic geometry, after the pioneering work of Tamarkin. In this talk, I will propose a new sheaf-theoretic method to estimate the displacement energy of compact subsets in cotangent bundles. In the course of the proof, we introduce a persistence-like pseudo-distance on Tamarkin's sheaf category. This is a joint work with Tomohiro Asano.

The microlocal sheaf theory due to Kashiwara and Schapira can be regarded as Morse theory with sheaf coefficients. Recently it has been applied to symplectic geometry, after the pioneering work of Tamarkin. In this talk, I will propose a new sheaf-theoretic method to estimate the displacement energy of compact subsets in cotangent bundles. In the course of the proof, we introduce a persistence-like pseudo-distance on Tamarkin's sheaf category. This is a joint work with Tomohiro Asano.

### 2018/01/29

#### Operator Algebra Seminars

16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)

Tingley's problem for operator algebras

**Michiya Mori**(Univ. Tokyo)Tingley's problem for operator algebras

#### Tokyo Probability Seminar

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

(JAPANESE)

**Kazuhiro Kuwae**(Department of Applied Mathematics, Faculty of Science, Fukuoka University)(JAPANESE)

### 2018/01/26

#### Colloquium

15:30-16:30 Room #002 (Graduate School of Math. Sci. Bldg.)

(JAPANESE)

**Yuta Koike**(Univ. Tokyo)(JAPANESE)

#### Algebraic Geometry Seminar

16:30-18:00 Room #122 (Graduate School of Math. Sci. Bldg.)

On classification of prime Q-Fano 3-folds with only 1/2(1,1,1)-singularities and of genus less than 2

**Hiromichi Takagi**(The University of Tokyo)On classification of prime Q-Fano 3-folds with only 1/2(1,1,1)-singularities and of genus less than 2

[ Abstract ]

I classified prime Q-Fano threefolds with only 1/2(1,1,1)-singularities and of genus greater than 1 (2002, Nagoya Math. J.).

In this talk, I will explain how the method in that paper can be extended to the case of genus less than 2. The method is so called two ray game. By this method, I can classify the possibilities of such Q-Fano's. The classification is not yet completed since constructions of examples in certain cases are difficult. I will also explain some pretty examples in this talk.

I classified prime Q-Fano threefolds with only 1/2(1,1,1)-singularities and of genus greater than 1 (2002, Nagoya Math. J.).

In this talk, I will explain how the method in that paper can be extended to the case of genus less than 2. The method is so called two ray game. By this method, I can classify the possibilities of such Q-Fano's. The classification is not yet completed since constructions of examples in certain cases are difficult. I will also explain some pretty examples in this talk.

### 2018/01/25

#### FMSP Lectures

15:00-16:30 Room #002 (Graduate School of Math. Sci. Bldg.)

NUMERICAL ANALYSIS, COBORDISM OF MANIFOLDS AND MONODROMY. (ENGLISH)

http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_ACampo.pdf

**Norbert A'Campo**(University of Basel)NUMERICAL ANALYSIS, COBORDISM OF MANIFOLDS AND MONODROMY. (ENGLISH)

[ Abstract ]

http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_ACampo_abst.pdf

[ Reference URL ]http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_ACampo_abst.pdf

http://fmsp.ms.u-tokyo.ac.jp/FMSPLectures_ACampo.pdf

### 2018/01/23

#### Tuesday Seminar on Topology

17:00-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

An invariant of 3-manifolds via homology cobordisms (JAPANESE)

**Yuta Nozaki**(The University of Tokyo)An invariant of 3-manifolds via homology cobordisms (JAPANESE)

[ Abstract ]

For a closed 3-manifold X, we consider the topological invariant defined as the minimal integer g such that X is obtained as the closure of a homology cobordism over a surface of genus g. We prove that the invariant equals one for every lens space, which is contrast to the fact that some lens spaces do not admit any open book decomposition whose page is a surface of genus one. The proof is based on the Chebotarev density theorem and binary quadratic forms in number theory.

For a closed 3-manifold X, we consider the topological invariant defined as the minimal integer g such that X is obtained as the closure of a homology cobordism over a surface of genus g. We prove that the invariant equals one for every lens space, which is contrast to the fact that some lens spaces do not admit any open book decomposition whose page is a surface of genus one. The proof is based on the Chebotarev density theorem and binary quadratic forms in number theory.

#### Tuesday Seminar on Topology

18:00-19:00 Room #056 (Graduate School of Math. Sci. Bldg.)

Wrapping projections and decompositions of Keinian groups (JAPANESE)

**Junha Tanaka**(The University of Tokyo)Wrapping projections and decompositions of Keinian groups (JAPANESE)

[ Abstract ]

Let $S$ be a closed surface of genus $g ¥geq 2$. The deformation space $AH(S)$ consists of (conjugacy classes of) discrete faithful representations $\rho:\pi_{1}(S) \to PSL_{2}(\mathbb{C})$.

McMullen, and Bromberg and Holt showed that $AH(S)$ can self-bump, that is, the interior of $AH(S)$ has the self-intersecting closure.

Both of them demonstrated the existence of self-bumping under the exisetence of a non-trivial wrapping projections from an algebraic limits to a geometric limits which wraps an annulus cusp into a torus cusp.

In this talk, given a representation $\rho$ at the boundary of $AH(S)$, we characterize a wrapping projection to a geometric limit associated to $\rho$, by the information of the actions of decomposed Kleinian groups of the image of $\rho$.

Let $S$ be a closed surface of genus $g ¥geq 2$. The deformation space $AH(S)$ consists of (conjugacy classes of) discrete faithful representations $\rho:\pi_{1}(S) \to PSL_{2}(\mathbb{C})$.

McMullen, and Bromberg and Holt showed that $AH(S)$ can self-bump, that is, the interior of $AH(S)$ has the self-intersecting closure.

Both of them demonstrated the existence of self-bumping under the exisetence of a non-trivial wrapping projections from an algebraic limits to a geometric limits which wraps an annulus cusp into a torus cusp.

In this talk, given a representation $\rho$ at the boundary of $AH(S)$, we characterize a wrapping projection to a geometric limit associated to $\rho$, by the information of the actions of decomposed Kleinian groups of the image of $\rho$.

### 2018/01/22

#### Seminar on Geometric Complex Analysis

10:30-12:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Recent topics on the study of the Gauss images of minimal surfaces

**Yu Kawakami**(Kanazawa University)Recent topics on the study of the Gauss images of minimal surfaces

[ Abstract ]

In this talk, we give a survey of recent advances on the study of the images of the Gauss maps of complete minimal surfaces in Euclidean space.

In this talk, we give a survey of recent advances on the study of the images of the Gauss maps of complete minimal surfaces in Euclidean space.

#### Operator Algebra Seminars

16:45-18:15 Room #126 (Graduate School of Math. Sci. Bldg.)

On Cauchy noise loss in a stochastic parameter optimization of random matrices

**Tomohiro Hayase**(Univ. Tokyo)On Cauchy noise loss in a stochastic parameter optimization of random matrices

#### Tokyo Probability Seminar

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

(JAPANESE)

**Makiko Sasada**(Graduate School of Mathematical Science, the University of Tokyo)(JAPANESE)

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