## Seminar information archive

Seminar information archive ～02/17｜Today's seminar 02/18 | Future seminars 02/19～

### 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)

### 2011/01/19

#### Seminar on Mathematics for various disciplines

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

Exploration of essence of Mullins equation (JAPANESE)

**Yoshihito Ogasawara**(Waseda University Faculty of Science and Engineering)Exploration of essence of Mullins equation (JAPANESE)

#### Seminar on Probability and Statistics

15:00-16:10 Room #000 (Graduate School of Math. Sci. Bldg.)

Notes on estimating the probability of ruin and some generalization (JAPANESE)

[ Reference URL ]

http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/06.html

**SHIMIZU, Yasutaka**(Osaka University)Notes on estimating the probability of ruin and some generalization (JAPANESE)

[ Reference URL ]

http://www.ms.u-tokyo.ac.jp/~kengok/statseminar/2010/06.html

### 2011/01/18

#### Operator Algebra Seminars

16:30-18:00 Room #118 (Graduate School of Math. Sci. Bldg.)

Scattering induced current in a tight binding band (ENGLISH)

**Claude-Alain Pillet**(Univ. de Toulon et du Var)Scattering induced current in a tight binding band (ENGLISH)

#### Lie Groups and Representation Theory

17:00-18:00 Room #126 (Graduate School of Math. Sci. Bldg.)

Connections between Noncommutative Geometry and Lie groups

representations (ENGLISH)

**Pierre Clare**(Universite Orleans and the University of Tokyo)Connections between Noncommutative Geometry and Lie groups

representations (ENGLISH)

[ Abstract ]

One of the principles of Noncommutative Geometry is to study singular spaces that the tools of classical analysis like algebras of continuous functions fail to describe, replacing them by more general C*-algebras. After recalling fundamental facts about C*-algebras, Hilbert modules and group C*-algebras, we will present constructions and results aiming to understand principal series representations and Knapp-Stein theory in the noncommutative geometrical framework. Eventually we will explain the relationship between the analysis of reduced group C*-algebras and the computation of the Connes-Kasparov isomorphisms.

One of the principles of Noncommutative Geometry is to study singular spaces that the tools of classical analysis like algebras of continuous functions fail to describe, replacing them by more general C*-algebras. After recalling fundamental facts about C*-algebras, Hilbert modules and group C*-algebras, we will present constructions and results aiming to understand principal series representations and Knapp-Stein theory in the noncommutative geometrical framework. Eventually we will explain the relationship between the analysis of reduced group C*-algebras and the computation of the Connes-Kasparov isomorphisms.

### 2011/01/17

#### Algebraic Geometry Seminar

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

L^2 methods and Skoda division theorems (ENGLISH)

**Dano Kim**(KIAS)L^2 methods and Skoda division theorems (ENGLISH)

[ Abstract ]

Extension of Ohsawa-Takegoshi type and division of Skoda type are two important consequences of the L^2 methods of Hormander, Demailly and others. They are analogous to vanishing theorems of Kodaira type and can be viewed as some refinement of the vanishing. The best illustration of their usefulness up to now is Siu’s proof of invariance of plurigenera without general type assumption. In this talk, we will focus on the division theorem / problem and talk about its currently known cases (old and new). One motivation comes from yet another viewpoint on the finite generation of canonical ring.

Extension of Ohsawa-Takegoshi type and division of Skoda type are two important consequences of the L^2 methods of Hormander, Demailly and others. They are analogous to vanishing theorems of Kodaira type and can be viewed as some refinement of the vanishing. The best illustration of their usefulness up to now is Siu’s proof of invariance of plurigenera without general type assumption. In this talk, we will focus on the division theorem / problem and talk about its currently known cases (old and new). One motivation comes from yet another viewpoint on the finite generation of canonical ring.

#### Seminar on Geometric Complex Analysis

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

Asymptotics of the Bergman function for semipositive holomorphic line bundles (JAPANESE)

**Toshihiro Nose**(Kyushu Univ.)Asymptotics of the Bergman function for semipositive holomorphic line bundles (JAPANESE)

[ Abstract ]

In this talk, an asymptotic expansion of the Bergman function at a degenerate point is given for high powers of semipositive holomorphic line bundles on compact Kahler manifolds, whose Hermitian metric has some kind of quasihomogeneous properties. In the sence of pointwise asymptotics, This expansion is a generalization of the expansion of Tian-Zelditch-Catlin-Lu in the positive line bundle case.

In this talk, an asymptotic expansion of the Bergman function at a degenerate point is given for high powers of semipositive holomorphic line bundles on compact Kahler manifolds, whose Hermitian metric has some kind of quasihomogeneous properties. In the sence of pointwise asymptotics, This expansion is a generalization of the expansion of Tian-Zelditch-Catlin-Lu in the positive line bundle case.

### 2011/01/13

#### Operator Algebra Seminars

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

Global dimensions for fusion categories of type $(G,k)$ (ENGLISH)

**Robert Coquereaux**(CNRS/CPT)Global dimensions for fusion categories of type $(G,k)$ (ENGLISH)

### 2011/01/12

#### Number Theory Seminar

16:30-18:45 Room #056 (Graduate School of Math. Sci. Bldg.)

On regularized double shuffle relation for multiple zeta values (ENGLISH)

Spines with View Toward Modular Forms (ENGLISH)

**Zhonghua Li**(University of Tokyo) 16:30-17:30On regularized double shuffle relation for multiple zeta values (ENGLISH)

[ Abstract ]

Multiple zeta values(MZVs) are natural generalizations of Riemann zeta values. There are many rational relations among MZVs. It is conjectured that the regularized double shuffle relations contian all rational relations of MZVs. So other rational relations should be deduced from regularized dhouble shuffle relations. In this talk, we discuss some results on this problem. We define the gamma series accociated to elements satisfying regularized double shuffle relations and give some properties. Moreover we show that the Ohno-Zagier relations can be deduced from regularized double shuffle relations.

Multiple zeta values(MZVs) are natural generalizations of Riemann zeta values. There are many rational relations among MZVs. It is conjectured that the regularized double shuffle relations contian all rational relations of MZVs. So other rational relations should be deduced from regularized dhouble shuffle relations. In this talk, we discuss some results on this problem. We define the gamma series accociated to elements satisfying regularized double shuffle relations and give some properties. Moreover we show that the Ohno-Zagier relations can be deduced from regularized double shuffle relations.

**Dan Yasaki**(North Carolina University) 17:45-18:45Spines with View Toward Modular Forms (ENGLISH)

[ Abstract ]

The study of an arithmetic group is often aided by the fact that it acts naturally on a nice topological object. One can then use topological or geometric techniques to try to recover arithmetic data. For example, one often studies SL_2(Z) in terms of

its action on the upper half plane. In this talk, we will examine spines, which are the ``smallest" such spaces for a given arithmetic group. On overview of some known theoretical results and explicit computations will be given.

The study of an arithmetic group is often aided by the fact that it acts naturally on a nice topological object. One can then use topological or geometric techniques to try to recover arithmetic data. For example, one often studies SL_2(Z) in terms of

its action on the upper half plane. In this talk, we will examine spines, which are the ``smallest" such spaces for a given arithmetic group. On overview of some known theoretical results and explicit computations will be given.

### 2011/01/11

#### Tuesday Seminar on Topology

16:30-18:00 Room #056 (Graduate School of Math. Sci. Bldg.)

The Chas-Sullivan conjecture for a surface of infinite genus (JAPANESE)

**Nariya Kawazumi**(The University of Tokyo)The Chas-Sullivan conjecture for a surface of infinite genus (JAPANESE)

[ Abstract ]

Let \\Sigma_{\\infty,1} be the inductive limit of compact

oriented surfaces with one boundary component. We prove the

center of the Goldman Lie algebra of the surface \\Sigma_{\\infty,1}

is spanned by the constant loop.

A similar statement for a closed oriented surface was conjectured

by Chas and Sullivan, and proved by Etingof. Our result is deduced

from a computation of the center of the Lie algebra of oriented chord

diagrams.

If time permits, the Lie bracket on the space of linear chord diagrams

will be discussed. This talk is based on a joint work with Yusuke Kuno

(Hiroshima U./JSPS).

Let \\Sigma_{\\infty,1} be the inductive limit of compact

oriented surfaces with one boundary component. We prove the

center of the Goldman Lie algebra of the surface \\Sigma_{\\infty,1}

is spanned by the constant loop.

A similar statement for a closed oriented surface was conjectured

by Chas and Sullivan, and proved by Etingof. Our result is deduced

from a computation of the center of the Lie algebra of oriented chord

diagrams.

If time permits, the Lie bracket on the space of linear chord diagrams

will be discussed. This talk is based on a joint work with Yusuke Kuno

(Hiroshima U./JSPS).

#### Operator Algebra Seminars

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

Noncommutative geometry and diffeomorphism-invariant geometries (ENGLISH)

**Raphael Ponge**(Univ. Tokyo)Noncommutative geometry and diffeomorphism-invariant geometries (ENGLISH)

#### Numerical Analysis Seminar

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

Norm estimates of inverse linear ordinary differential operator and its applications (JAPANESE)

[ Reference URL ]

http://www.infsup.jp/utnas/

**Takehiko Kinoshita**(RIMS)Norm estimates of inverse linear ordinary differential operator and its applications (JAPANESE)

[ Reference URL ]

http://www.infsup.jp/utnas/

### 2010/12/22

#### GCOE Seminars

11:00-12:00 Room #570 (Graduate School of Math. Sci. Bldg.)

Stability estimates for the anisotropic Schrodinger equations from the Dirichlet to Neumann map (ENGLISH)

**Mourad Bellassoued**(Faculté des Sciences de Bizerte)Stability estimates for the anisotropic Schrodinger equations from the Dirichlet to Neumann map (ENGLISH)

[ Abstract ]

In this talk we want to obtain stability estimates for the inverse problem of determining the electric potential or the conformal factor in the Schrodinger equations in an anisotropic media with Dirichlet data from measured Neumann boundary observations. This information is enclosed in the dynamical Dirichlet-to-Neumann map associated to the Schrödinger equation. We prove in dimension $n\\geq 2$ that the knowledge of the Dirichlet to Neumann map for the Schrödinger equation measured on the boundary uniquely determines the electric potential and we prove H\\"older-type stability in determining the potential. We prove similar results for the determination of a conformal factor close to 1 (this is a joint work with David Dos Santos Ferreira).

In this talk we want to obtain stability estimates for the inverse problem of determining the electric potential or the conformal factor in the Schrodinger equations in an anisotropic media with Dirichlet data from measured Neumann boundary observations. This information is enclosed in the dynamical Dirichlet-to-Neumann map associated to the Schrödinger equation. We prove in dimension $n\\geq 2$ that the knowledge of the Dirichlet to Neumann map for the Schrödinger equation measured on the boundary uniquely determines the electric potential and we prove H\\"older-type stability in determining the potential. We prove similar results for the determination of a conformal factor close to 1 (this is a joint work with David Dos Santos Ferreira).

#### Number Theory Seminar

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

Inductive construction of the p-adic zeta functions for non-commutative

p-extensions of totally real fields with exponent p (JAPANESE)

**Takashi Hara**(University of Tokyo)Inductive construction of the p-adic zeta functions for non-commutative

p-extensions of totally real fields with exponent p (JAPANESE)

[ Abstract ]

We will discuss how to construct p-adic zeta functions and verify

the main conjecture in special cases in non-commutative Iwasawa theory

for totally real number fields.

The non-commutative Iwasawa main conjecture for totally real number

fields has been verified in special cases by Kazuya Kato,

Mahesh Kakde and the speaker by `patching method of p-adic zeta functions'

introduced by David Burns and Kazuya Kato (Jurgen Ritter and Alfred Weiss

have also constructed the successful example of the main conjecture

under somewhat different formulations).

In this talk we will explain that we can prove the main conjecture

for cases where the Galois group is isomorphic

to the direct product of the ring of p-adic integer and a finite p-group

of exponent p by utilizing Burns-Kato's method and inductive arguments.

Finally we remark that in 2010 Ritter-Weiss and Kakde independently

justified the non-commutative main conjecture

for totally real number fields under general settings.

We will discuss how to construct p-adic zeta functions and verify

the main conjecture in special cases in non-commutative Iwasawa theory

for totally real number fields.

The non-commutative Iwasawa main conjecture for totally real number

fields has been verified in special cases by Kazuya Kato,

Mahesh Kakde and the speaker by `patching method of p-adic zeta functions'

introduced by David Burns and Kazuya Kato (Jurgen Ritter and Alfred Weiss

have also constructed the successful example of the main conjecture

under somewhat different formulations).

In this talk we will explain that we can prove the main conjecture

for cases where the Galois group is isomorphic

to the direct product of the ring of p-adic integer and a finite p-group

of exponent p by utilizing Burns-Kato's method and inductive arguments.

Finally we remark that in 2010 Ritter-Weiss and Kakde independently

justified the non-commutative main conjecture

for totally real number fields under general settings.

### 2010/12/21

#### Lie Groups and Representation Theory

16:30-18:00 Room #126 (Graduate School of Math. Sci. Bldg.)

Some relation between the Weyl module and the crystal basis of the tensor product of fudamental representations (ENGLISH)

**Katsuyuki NAOI**(Graduate School of Mathematical Sciences, the University of Tokyo)Some relation between the Weyl module and the crystal basis of the tensor product of fudamental representations (ENGLISH)

### 2010/12/20

#### Seminar on Geometric Complex Analysis

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

Pseudoconvex domains in Hopf surfaces (JAPANESE)

**Hiroshi Yamaguchi**(Shiga Univ*)Pseudoconvex domains in Hopf surfaces (JAPANESE)

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