## Seminar information archive

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

### 2011/02/03

#### thesis presentations

09:45-11:00 Room #118 (Graduate School of Math. Sci. Bldg.)

Generators of modules in tropical geometry(トロピカル幾何における加群の生成元) (JAPANESE)

**Shuhei YOSHITOMI**(Graduate School of Mathematical Sciences the University of Tokyo)Generators of modules in tropical geometry(トロピカル幾何における加群の生成元) (JAPANESE)

#### thesis presentations

11:00-12:15 Room #118 (Graduate School of Math. Sci. Bldg.)

Finite Symplectic Actions on the K3 Lattice(K3格子への有限シンプレクティック作用) (JAPANESE)

**Kenji HASHIMOTO**(Graduate School of Mathematical Sciences University of Tokyo)Finite Symplectic Actions on the K3 Lattice(K3格子への有限シンプレクティック作用) (JAPANESE)

#### thesis presentations

13:00-14:15 Room #118 (Graduate School of Math. Sci. Bldg.)

Weyl modules, Demazure modules and finite crystals for non-simply laced type(Bn, Cn, F4, G2型のワイル加群、デマズール加群および有限クリスタルについて) (JAPANESE)

**Katsuyuki NAOI**(Graduate School of Mathematical Sciences University of Tokyo)Weyl modules, Demazure modules and finite crystals for non-simply laced type(Bn, Cn, F4, G2型のワイル加群、デマズール加群および有限クリスタルについて) (JAPANESE)

#### thesis presentations

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

Extensions between finite-dimensional simple modules over a generalized current Lie algebra(一般化されたカレントリー代数上の有限次元単純加群の間の拡大) (JAPANESE)

**Ryosuke KODERA**(Graduate School of Mathematical Sciences University of Tokyo )Extensions between finite-dimensional simple modules over a generalized current Lie algebra(一般化されたカレントリー代数上の有限次元単純加群の間の拡大) (JAPANESE)

#### thesis presentations

09:45-11:00 Room #122 (Graduate School of Math. Sci. Bldg.)

Rigidity theorems for universal and symplectic universal lattices(普遍格子と斜交普遍格子の剛性定理) (JAPANESE)

**Masato MIMURA**(Graduate School of Mathematical Sciences University of Tokyo)Rigidity theorems for universal and symplectic universal lattices(普遍格子と斜交普遍格子の剛性定理) (JAPANESE)

#### thesis presentations

11:00-12:15 Room #122 (Graduate School of Math. Sci. Bldg.)

Deformation of torus equivariant spectral triples(トーラス同変なスペクトラル三つ組の変形) (JAPANESE)

**Makoto YAMASHITA**(Graduate School of Mathematical Sciences University of Tokyo)Deformation of torus equivariant spectral triples(トーラス同変なスペクトラル三つ組の変形) (JAPANESE)

#### thesis presentations

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

Noncommutative Maximal Ergodic Inequality For Non-tracial L1-spaces(非トレース的L1空間に対する非可換極大エルゴード不等式) (JAPANESE)

**Zhang Qin**(Graduate School of Mathematical Sciences University of Tokyo)Noncommutative Maximal Ergodic Inequality For Non-tracial L1-spaces(非トレース的L1空間に対する非可換極大エルゴード不等式) (JAPANESE)

#### thesis presentations

14:15-15:30 Room #128 (Graduate School of Math. Sci. Bldg.)

Dispersive and Strichartz estimates for Schrödinger equations(シュレディンガー方程式に対する分散型及びストリッカーツ評価) (JAPANESE)

**Haruya MIZUTANI**(Graduate School of Mathematical Sciences University of Tokyo)Dispersive and Strichartz estimates for Schrödinger equations(シュレディンガー方程式に対する分散型及びストリッカーツ評価) (JAPANESE)

#### thesis presentations

15:45-17:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Conditional stability by Carleman estimates for inverse problems : coefficient inverse problems for the Dirac equation, the determination of subboundary by the heat equation and the continuation of solution of the Euler equation(逆問題に対するカーレマン評価による条件付き安定性: ディラック方程式に対する係数逆問題,熱方程式による部分境界の決定とオイラー方程式に対する解の接続性) (JAPANESE)

**Atsushi KAWAMOTO**(Graduate School of Mathematical Sciences University of Tokyo)Conditional stability by Carleman estimates for inverse problems : coefficient inverse problems for the Dirac equation, the determination of subboundary by the heat equation and the continuation of solution of the Euler equation(逆問題に対するカーレマン評価による条件付き安定性: ディラック方程式に対する係数逆問題,熱方程式による部分境界の決定とオイラー方程式に対する解の接続性) (JAPANESE)

### 2011/02/02

#### Lectures

16:30-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)

Connectedness of a level set and a generalization of Oleinik and Aronson-Benilan type one-sided inequalities (ENGLISH)

**Yong Jung Kim**(Korea Advanced Institute of Science and Technology (KAIST))Connectedness of a level set and a generalization of Oleinik and Aronson-Benilan type one-sided inequalities (ENGLISH)

[ Abstract ]

The one-sided Oleinik inequality provides the uniqueness and a sharp regularity of solutions to a scalar conservation law. The Aronson-Benilan type one-sided inequalities also play a similar role. We will discuss about their generalization to a general setting.

The one-sided Oleinik inequality provides the uniqueness and a sharp regularity of solutions to a scalar conservation law. The Aronson-Benilan type one-sided inequalities also play a similar role. We will discuss about their generalization to a general setting.

#### Lectures

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

Regularity of two dimensional capillary gravity water waves (ENGLISH)

**Guanghui ZHANG**(Graduate School of Mathematical Sciences, the University of Tokyo)Regularity of two dimensional capillary gravity water waves (ENGLISH)

[ Abstract ]

We consider the two-dimensional steady capillary water waves with vorticity. In the case of zero surface tension, it is well known that the free surface of a wave of maximal amplitude is not smooth at a free surface point of maximal height, but forms a sharp crest with an angle of 120 degrees. When the surface tension is not zero, physical intuition suggests that the corner singularities should disappear. In this talk we prove that for suitable weak solutions, the free surfaces are smooth. On a technical level, solutions of our problem are closely related to critical points of the Mumford-Shah functional, so that our main task is to exclude cusps pointing into the water phase. This is a joint work with Georg Weiss.

We consider the two-dimensional steady capillary water waves with vorticity. In the case of zero surface tension, it is well known that the free surface of a wave of maximal amplitude is not smooth at a free surface point of maximal height, but forms a sharp crest with an angle of 120 degrees. When the surface tension is not zero, physical intuition suggests that the corner singularities should disappear. In this talk we prove that for suitable weak solutions, the free surfaces are smooth. On a technical level, solutions of our problem are closely related to critical points of the Mumford-Shah functional, so that our main task is to exclude cusps pointing into the water phase. This is a joint work with Georg Weiss.

#### Seminar on Probability and Statistics

15:00-16:10 Room #006 (Graduate School of Math. Sci. Bldg.)

An Attempt to formalize Statistical Inferences for Weakly Dependent Time-Series Data and Some Trials for Statistical Analysis of Financial Data (JAPANESE)

[ Reference URL ]

http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/08.html

**MIURA, Ryozo**(Hitotsubashi University)An Attempt to formalize Statistical Inferences for Weakly Dependent Time-Series Data and Some Trials for Statistical Analysis of Financial Data (JAPANESE)

[ Reference URL ]

http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/08.html

### 2011/01/31

#### Algebraic Geometry Seminar

16:40-18:10 Room #126 (Graduate School of Math. Sci. Bldg.)

Restriction maps to the Coble quartic (ENGLISH)

**Sukmoon Huh**(KIAS)Restriction maps to the Coble quartic (ENGLISH)

[ Abstract ]

The Coble sixfold quartic is the moduli space of semi-stable vector bundle of rank 2 on a non-hyperelliptic curve of genus 3 with canonical determinant. Considering the curve as a plane quartic, we investigate the restriction of the semi-stable sheaves over the projective plane to the curve. We suggest a positive side of this trick in the study of the moduli space of vector bundles over curves by showing several examples such as Brill-Noether loci and a few rational subvarieties of the Coble quartic. In a later part of the talk, we introduce the rationality problem of the Coble quartic. If the time permits, we will apply the same idea to the moduli space of bundles over curves of genus 4 to derive some geometric properties of the Brill-Noether loci in the case of genus 4.

The Coble sixfold quartic is the moduli space of semi-stable vector bundle of rank 2 on a non-hyperelliptic curve of genus 3 with canonical determinant. Considering the curve as a plane quartic, we investigate the restriction of the semi-stable sheaves over the projective plane to the curve. We suggest a positive side of this trick in the study of the moduli space of vector bundles over curves by showing several examples such as Brill-Noether loci and a few rational subvarieties of the Coble quartic. In a later part of the talk, we introduce the rationality problem of the Coble quartic. If the time permits, we will apply the same idea to the moduli space of bundles over curves of genus 4 to derive some geometric properties of the Brill-Noether loci in the case of genus 4.

#### Kavli IPMU Komaba Seminar

16:30-18:00 Room #002 (Graduate School of Math. Sci. Bldg.)

Mirror symmetry for toric Calabi-Yau manifolds from the SYZ viewpoint (ENGLISH)

**Kwok-Wai Chan**(IPMU, the University of Tokyo)Mirror symmetry for toric Calabi-Yau manifolds from the SYZ viewpoint (ENGLISH)

[ Abstract ]

In this talk, I will discuss mirror symmetry for toric

Calabi-Yau (CY) manifolds from the viewpoint of the SYZ program. I will

start with a special Lagrangian torus fibration on a toric CY manifold,

and then construct its instanton-corrected mirror by a T-duality modified

by quantum corrections. A remarkable feature of this construction is that

the mirror family is inherently written in canonical flat coordinates. As

a consequence, we get a conjectural enumerative meaning for the inverse

mirror maps. If time permits, I will explain the verification of this

conjecture in several examples via a formula which computes open

Gromov-Witten invariants for toric manifolds.

In this talk, I will discuss mirror symmetry for toric

Calabi-Yau (CY) manifolds from the viewpoint of the SYZ program. I will

start with a special Lagrangian torus fibration on a toric CY manifold,

and then construct its instanton-corrected mirror by a T-duality modified

by quantum corrections. A remarkable feature of this construction is that

the mirror family is inherently written in canonical flat coordinates. As

a consequence, we get a conjectural enumerative meaning for the inverse

mirror maps. If time permits, I will explain the verification of this

conjecture in several examples via a formula which computes open

Gromov-Witten invariants for toric manifolds.

#### Seminar on Geometric Complex Analysis

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

Varieties with ample cotangent bundle and hyperbolicity (ENGLISH)

**Damian Brotbek**(Rennes Univ.)Varieties with ample cotangent bundle and hyperbolicity (ENGLISH)

[ Abstract ]

Varieties with ample cotangent bundle satisfy many interesting properties and are supposed to be abundant, however relatively few concrete examples are known. In this talk we will construct such examples as complete intersection surfaces in projective space, and explain how this problem is related to the study of hyperbolicity properties for hypersurfaces.

Varieties with ample cotangent bundle satisfy many interesting properties and are supposed to be abundant, however relatively few concrete examples are known. In this talk we will construct such examples as complete intersection surfaces in projective space, and explain how this problem is related to the study of hyperbolicity properties for hypersurfaces.

### 2011/01/28

#### Colloquium

16:30-17:30 Room #117 (Graduate School of Math. Sci. Bldg.)

Conformal invariance in probability theory (JAPANESE)

**Shirai Tomoyuki**(Kyushu University)Conformal invariance in probability theory (JAPANESE)

#### Operator Algebra Seminars

14:45-16:15 Room #122 (Graduate School of Math. Sci. Bldg.)

Semiprojectivity of graph algebras (ENGLISH)

**Takeshi Katsura**(Keio University)Semiprojectivity of graph algebras (ENGLISH)

### 2011/01/27

#### Operator Algebra Seminars

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

Entire Cyclic Cohomology of Noncommutative Riemann Surfaces (JAPANESE)

**Hiroshi Takai**(Tokyo Metropolitan University)Entire Cyclic Cohomology of Noncommutative Riemann Surfaces (JAPANESE)

#### Applied Analysis

16:00-17:30 Room #002 (Graduate School of Math. Sci. Bldg.)

Attraction at infinity: Constructing non-compact global attractors in the slowly non-dissipative realm (ENGLISH)

**Nitsan Ben-Gal**(The Weizmann Institute of Science)Attraction at infinity: Constructing non-compact global attractors in the slowly non-dissipative realm (ENGLISH)

[ Abstract ]

One of the primary tools for understanding the much-studied realm of reaction-diffusion equations is the global attractor, which provides us with a qualitative understanding of the governing behaviors of solutions to the equation in question. Nevertheless, the classic global attractor for such systems is defined to be compact, and thus attractor theory has previously excluded such analysis from being applied to non-dissipative reaction-diffusion equations.

In this talk I will present recent results in which I developed a non-compact analogue to the classical global attractor, and will discuss the methods derived in order to obtain a full decomposition of the non-compact global attractor for a slowly non-dissipative reaction-diffusion equation. In particular, attention will be paid to the nodal property techniques and reduction methods which form a critical underpinning of asymptotics research in both dissipative and non-dissipative evolutionary equations. I will discuss the concepts of the ‘completed inertial manifold’ and ‘non-compact global attractor’, and show how these in particular allow us to produce equivalent results for a class of slowly non-dissipative equations as have been achieved for dissipative equations. Additionally, I will address the behavior of solutions to slowly non-dissipative equations approaching and at infinity, the realm which presents both the challenges and rewards of removing the necessity of dissipativity.

One of the primary tools for understanding the much-studied realm of reaction-diffusion equations is the global attractor, which provides us with a qualitative understanding of the governing behaviors of solutions to the equation in question. Nevertheless, the classic global attractor for such systems is defined to be compact, and thus attractor theory has previously excluded such analysis from being applied to non-dissipative reaction-diffusion equations.

In this talk I will present recent results in which I developed a non-compact analogue to the classical global attractor, and will discuss the methods derived in order to obtain a full decomposition of the non-compact global attractor for a slowly non-dissipative reaction-diffusion equation. In particular, attention will be paid to the nodal property techniques and reduction methods which form a critical underpinning of asymptotics research in both dissipative and non-dissipative evolutionary equations. I will discuss the concepts of the ‘completed inertial manifold’ and ‘non-compact global attractor’, and show how these in particular allow us to produce equivalent results for a class of slowly non-dissipative equations as have been achieved for dissipative equations. Additionally, I will address the behavior of solutions to slowly non-dissipative equations approaching and at infinity, the realm which presents both the challenges and rewards of removing the necessity of dissipativity.

### 2011/01/26

#### Number Theory Seminar

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

The p-adic Gross-Zagier formula for elliptic curves at supersingular primes (JAPANESE)

**Shinichi Kobayashi**(Tohoku University)The p-adic Gross-Zagier formula for elliptic curves at supersingular primes (JAPANESE)

[ Abstract ]

The p-adic Gross-Zagier formula is a formula relating the derivative of the p-adic L-function of elliptic curves to the p-adic height of Heegner points. For a good ordinary prime p, the formula is proved by B. Perrin-Riou more than 20 years ago. Recently, the speaker proved it for a supersingular prime p. In this talk, he explains the proof.

The p-adic Gross-Zagier formula is a formula relating the derivative of the p-adic L-function of elliptic curves to the p-adic height of Heegner points. For a good ordinary prime p, the formula is proved by B. Perrin-Riou more than 20 years ago. Recently, the speaker proved it for a supersingular prime p. In this talk, he explains the proof.

#### PDE Real Analysis Seminar

10:30-11:30 Room #056 (Graduate School of Math. Sci. Bldg.)

)

Quenching Problem Arising in Micro-electro Mechanical Systems

(JAPANESE)

**Jong-Shenq Guo**(Department of Mathematics, Tamkang University)

Quenching Problem Arising in Micro-electro Mechanical Systems

(JAPANESE)

[ Abstract ]

In this talk, we shall present some recent results on quenching problems which arise in Micro-electro Mechanical Systems.

We shall also give some open problems in this research area.

In this talk, we shall present some recent results on quenching problems which arise in Micro-electro Mechanical Systems.

We shall also give some open problems in this research area.

#### Seminar on Probability and Statistics

15:00-16:10 Room #002 (Graduate School of Math. Sci. Bldg.)

Semi-parametric profile likelihood estimation and implicitly defined functions (JAPANESE)

http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/07.html

**HIROSE, Yuichi**(Victoria University of Wellington)Semi-parametric profile likelihood estimation and implicitly defined functions (JAPANESE)

[ Abstract ]

The object of talk is the differentiability of implicitly defined functions which we

encounter in the profile likelihood estimation of parameters in semi-parametric models. Scott and Wild

(1997, 2001) and Murphy and Vaart (2000) developed methodologies that can avoid dealing with such implicitly

defined functions by reparametrizing parameters in the profile likelihood and using an approximate least

favorable submodel in semi-parametric models. Our result shows applicability of an alternative approach

developed in Hirose (2010) which uses the differentiability of implicitly defined functions.

[ Reference URL ]The object of talk is the differentiability of implicitly defined functions which we

encounter in the profile likelihood estimation of parameters in semi-parametric models. Scott and Wild

(1997, 2001) and Murphy and Vaart (2000) developed methodologies that can avoid dealing with such implicitly

defined functions by reparametrizing parameters in the profile likelihood and using an approximate least

favorable submodel in semi-parametric models. Our result shows applicability of an alternative approach

developed in Hirose (2010) which uses the differentiability of implicitly defined functions.

http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/07.html

### 2011/01/25

#### Tuesday Seminar on Topology

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

On unknotting of surface-knots with small sheet numbers

(JAPANESE)

**Chikara Haruta**(Graduate School of Mathematical Sciences, the University of Tokyo )On unknotting of surface-knots with small sheet numbers

(JAPANESE)

[ Abstract ]

A connected surface smoothly embedded in ${\\mathbb R}^4$ is called a surface-knot. In particular, if a surface-knot $F$ is homeomorphic to the $2$-sphere or the torus, then it is called an $S^2$-knot or a $T^2$-knot, respectively. The sheet number of a surface-knot is an invariant analogous to the crossing number of a $1$-knot. M. Saito and S. Satoh proved some results concerning the sheet number of an $S^2$-knot. In particular, it is known that an $S^2$-knot is trivial if and only if its sheet number is $1$, and there is no $S^2$-knot whose sheet number is $2$. In this talk, we show that there is no $S^2$-knot whose sheet number is $3$, and a $T^2$-knot is trivial if and only if its sheet number is $1$.

A connected surface smoothly embedded in ${\\mathbb R}^4$ is called a surface-knot. In particular, if a surface-knot $F$ is homeomorphic to the $2$-sphere or the torus, then it is called an $S^2$-knot or a $T^2$-knot, respectively. The sheet number of a surface-knot is an invariant analogous to the crossing number of a $1$-knot. M. Saito and S. Satoh proved some results concerning the sheet number of an $S^2$-knot. In particular, it is known that an $S^2$-knot is trivial if and only if its sheet number is $1$, and there is no $S^2$-knot whose sheet number is $2$. In this talk, we show that there is no $S^2$-knot whose sheet number is $3$, and a $T^2$-knot is trivial if and only if its sheet number is $1$.

### 2011/01/24

#### Seminar on Geometric Complex Analysis

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

Toward a complex analytic 3-dimensional Kleinian group theory (JAPANESE)

**Masahide Kato**(Sophia Univ.)Toward a complex analytic 3-dimensional Kleinian group theory (JAPANESE)

### 2011/01/20

#### Operator Algebra Seminars

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

Property (TT)/T and homomorphism rigidity into Out$(F_n)$ (JAPANESE)

**Masato Mimura**(Univ. Tokyo)Property (TT)/T and homomorphism rigidity into Out$(F_n)$ (JAPANESE)

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