## Seminar information archive

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

### 2013/10/08

#### Tuesday Seminar on Topology

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

An invariant of rational homology 3-spheres via vector fields. (JAPANESE)

**Tatsuro Shimizu**(The Univesity of Tokyo)An invariant of rational homology 3-spheres via vector fields. (JAPANESE)

[ Abstract ]

In this talk, we define an invariant of rational homology 3-spheres with

values in a space $\\mathcal A(\\emptyset)$ of Jacobi diagrams by using

vector fields.

The construction of our invariant is a generalization of both that of

the Kontsevich-Kuperberg-Thurston invariant $z^{KKT}$

and that of Fukaya and Watanabe's Morse homotopy invariant $z^{FW}$.

As an application of our invariant, we prove that $z^{KKT}=z^{FW}$ for

integral homology 3-spheres.

In this talk, we define an invariant of rational homology 3-spheres with

values in a space $\\mathcal A(\\emptyset)$ of Jacobi diagrams by using

vector fields.

The construction of our invariant is a generalization of both that of

the Kontsevich-Kuperberg-Thurston invariant $z^{KKT}$

and that of Fukaya and Watanabe's Morse homotopy invariant $z^{FW}$.

As an application of our invariant, we prove that $z^{KKT}=z^{FW}$ for

integral homology 3-spheres.

### 2013/10/07

#### Seminar on Geometric Complex Analysis

10:30-12:00 Room #126 (Graduate School of Math. Sci. Bldg.)

The limits on boundary of orbifold Kähler-Einstein metrics and orbifold Kähler-Ricci flows over quasi-projective manifolds (JAPANESE)

**Shin Kikuta**(Sophia University)The limits on boundary of orbifold Kähler-Einstein metrics and orbifold Kähler-Ricci flows over quasi-projective manifolds (JAPANESE)

[ Abstract ]

In this talk, we consider a sequence of orbifold Kähler-Einstein metrics of negative Ricci curvature or corresponding orbifold normalized Kähler-Ricci flows on a quasi-projective manifold with ample log-canonical bundle for a simple normal crossing divisor. Tian-Yau, S. Bando and H. Tsuji established that the sequence of orbifold Kähler-Einstein metrics converged to the complete Käler-Einstein metric of negative Ricci curvature on the complement of the boundary divisor. The main purpose of this talk is to show that such a convergence is also true on the boundary for both of the orbifold Kähler-Einstein metrics and the orbifold normalized Kähler-Ricci flows.

In this talk, we consider a sequence of orbifold Kähler-Einstein metrics of negative Ricci curvature or corresponding orbifold normalized Kähler-Ricci flows on a quasi-projective manifold with ample log-canonical bundle for a simple normal crossing divisor. Tian-Yau, S. Bando and H. Tsuji established that the sequence of orbifold Kähler-Einstein metrics converged to the complete Käler-Einstein metric of negative Ricci curvature on the complement of the boundary divisor. The main purpose of this talk is to show that such a convergence is also true on the boundary for both of the orbifold Kähler-Einstein metrics and the orbifold normalized Kähler-Ricci flows.

### 2013/10/03

#### Geometry Colloquium

10:00-11:30 Room #122 (Graduate School of Math. Sci. Bldg.)

A rigidity lemma for cocycles over BS(1,k)-actions (JAPANESE)

**Masayuki ASAOKA**(Kyoto University)A rigidity lemma for cocycles over BS(1,k)-actions (JAPANESE)

[ Abstract ]

Existence of an invariant geometric structure is persistent for many known examples of group actions on homogeneous spaces. In this talk, I would like to report an attempt to explain such a rigidity from a unified point of view. We will see that some rigidity results are reduced to a rigidity lemma on Diff(R^n,0)-valued cocycles over BS(1,k)-actions, where BS(1,k) is the Baumslag-Solitar group .

Existence of an invariant geometric structure is persistent for many known examples of group actions on homogeneous spaces. In this talk, I would like to report an attempt to explain such a rigidity from a unified point of view. We will see that some rigidity results are reduced to a rigidity lemma on Diff(R^n,0)-valued cocycles over BS(1,k)-actions, where BS(1,k) is the Baumslag-Solitar group .

### 2013/10/02

#### Operator Algebra Seminars

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

A classification of flows on AFD factors with faithful Connes-Takesaki modules

(JAPANESE)

**Koichi Shimada**(Univ. Tokyo)A classification of flows on AFD factors with faithful Connes-Takesaki modules

(JAPANESE)

### 2013/10/01

#### Tuesday Seminar on Topology

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

The geography problem of Lefschetz fibrations (JAPANESE)

**Naoyuki Monden**(Tokyo University of Science)The geography problem of Lefschetz fibrations (JAPANESE)

[ Abstract ]

To consider holomorphic fibrations complex surfaces over complex curves

and Lefschetz fibrations over surfaces is one method for the study of

complex surfaces of general type and symplectic 4-manifods, respectively.

In this talk, by comparing the geography problem of relatively minimal

holomorphic fibrations with that of relatively minimal Lefschetz

fibrations (i.e., the characterization of pairs $(x,y)$ of certain

invariants $x$ and $y$ corresponding to relatively minimal holomorphic

fibrations and relatively minimal Lefschetz fibrations), we observe the

difference between complex surfaces of general type and symplectic

4-manifolds. In particular, we construct Lefschetz fibrations violating

the ``slope inequality" which holds for any relatively minimal holomorphic

fibrations.

To consider holomorphic fibrations complex surfaces over complex curves

and Lefschetz fibrations over surfaces is one method for the study of

complex surfaces of general type and symplectic 4-manifods, respectively.

In this talk, by comparing the geography problem of relatively minimal

holomorphic fibrations with that of relatively minimal Lefschetz

fibrations (i.e., the characterization of pairs $(x,y)$ of certain

invariants $x$ and $y$ corresponding to relatively minimal holomorphic

fibrations and relatively minimal Lefschetz fibrations), we observe the

difference between complex surfaces of general type and symplectic

4-manifolds. In particular, we construct Lefschetz fibrations violating

the ``slope inequality" which holds for any relatively minimal holomorphic

fibrations.

### 2013/09/10

#### Monthly Seminar on Arithmetic of Automorphic Forms

13:30-15:00 Room #123 (Graduate School of Math. Sci. Bldg.)

Counting automorphic representations (JAPANESE)

Counting automorphic representations II (Sept. 17) (JAPANESE)

**Yuval Flicker**(Ohio State Univ.) 13:30-15:00Counting automorphic representations (JAPANESE)

**Yuval Flicker**(Ohio State University) 13:30-15:00Counting automorphic representations II (Sept. 17) (JAPANESE)

### 2013/09/07

#### FMSP Lectures

15:00-16:30 Room #123 (Graduate School of Math. Sci. Bldg.)

Dominating representations by Fuchsian ones (ENGLISH)

**Bertrand Deroin**(University of Paris-Sud)Dominating representations by Fuchsian ones (ENGLISH)

[ Abstract ]

We will focus on the problem of dominating the translation lengths of a representation from a surface group to the isometries of a CAT(-1) space by the lengths induced by a hyperbolic structure on the surface. This is related to the construction of 3-dimensional anti-de-Sitter compact manifolds. This is a collaboration with Nicolas Tholozan.

We will focus on the problem of dominating the translation lengths of a representation from a surface group to the isometries of a CAT(-1) space by the lengths induced by a hyperbolic structure on the surface. This is related to the construction of 3-dimensional anti-de-Sitter compact manifolds. This is a collaboration with Nicolas Tholozan.

### 2013/08/12

#### Operator Algebra Seminars

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

Operator Algebraic Construction of Quantum Field Theory Models (ENGLISH)

**Roberto Longo**(Univ. Roma, Tor Vergata)Operator Algebraic Construction of Quantum Field Theory Models (ENGLISH)

#### FMSP Lectures

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

Operator Algebraic Construction of Quantum Field Theory Models (ENGLISH)

**Roberto Longo**(Univ. Roma, Tor Vergata)Operator Algebraic Construction of Quantum Field Theory Models (ENGLISH)

### 2013/08/09

#### Operator Algebra Seminars

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

Cellular automata and groups (ENGLISH)

**Tullio Ceccherini-Silberstein**(Univ. Sannio)Cellular automata and groups (ENGLISH)

### 2013/08/08

#### Operator Algebra Seminars

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

Phase Plane Operator Valued Probability Measures: Constructions and Random Evolution (ENGLISH)

**Demosthenes Ellinas**(Technical University of Crete)Phase Plane Operator Valued Probability Measures: Constructions and Random Evolution (ENGLISH)

### 2013/08/07

#### FMSP Lectures

16:00-17:00 Room #370 (Graduate School of Math. Sci. Bldg.)

Water waves over a random bottom (ENGLISH)

**Philippe Guyenne**(Univ. of Delaware)Water waves over a random bottom (ENGLISH)

[ Abstract ]

We present a Hamiltonian formulation for nonlinear surface water waves in the presence of a variable bottom. This formulation is based on a reduction of the problem to a lower-dimensional system involving boundary variables alone. To accomplish this, we express the Dirichlet-to-Neumann operator as a Taylor series in terms of the surface and bottom variations. This expansion is convenient for both asymptotic calculations and numerical simulations. First we apply this formulation to the asymptotic description of long waves over random topography. We show that the principal component of the solution can be described by a Korteweg-de Vries equation plus random phase corrections. We also derive an asymptotic expression for the scattered component. Finally numerical simulations will be shown to illustrate the theoretical results. This is joint work with Walter Craig and Catherine Sulem.

We present a Hamiltonian formulation for nonlinear surface water waves in the presence of a variable bottom. This formulation is based on a reduction of the problem to a lower-dimensional system involving boundary variables alone. To accomplish this, we express the Dirichlet-to-Neumann operator as a Taylor series in terms of the surface and bottom variations. This expansion is convenient for both asymptotic calculations and numerical simulations. First we apply this formulation to the asymptotic description of long waves over random topography. We show that the principal component of the solution can be described by a Korteweg-de Vries equation plus random phase corrections. We also derive an asymptotic expression for the scattered component. Finally numerical simulations will be shown to illustrate the theoretical results. This is joint work with Walter Craig and Catherine Sulem.

### 2013/07/29

#### Mathematical Biology Seminar

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

Characteristic changes by time delay in the solution of differential equation and their applications (JAPANESE)

**Yoichi Enatsu**(Graduate School of Mathematical Sciences, University of Tokyo)Characteristic changes by time delay in the solution of differential equation and their applications (JAPANESE)

### 2013/07/26

#### thesis presentations

13:00-14:15 Room #122 (Graduate School of Math. Sci. Bldg.)

Examples of factors which have no Cartan subalgebras(カルタン部分環を持たない因子環の例) (JAPANESE)

**Yusuke ISONO**(Guraduate School of Mathematical Sciences the University of Tokyo)Examples of factors which have no Cartan subalgebras(カルタン部分環を持たない因子環の例) (JAPANESE)

#### FMSP Lectures

10:30-12:00 Room #118 (Graduate School of Math. Sci. Bldg.)

Representations of reductive groups and L-functions (II) (ENGLISH)

**Birgit Speh**(Cornell University)Representations of reductive groups and L-functions (II) (ENGLISH)

[ Abstract ]

In the second lecture we will quickly discuss Rankin Selberg integral approach to L-factors and then Shahidi's method of constructing L-functions by relating them to intertwining operators, leading to the definition of the the L-factors of tempered non degenerate representations. The lecture closes with a discussion of L-factors for nontempered representations.

In the second lecture we will quickly discuss Rankin Selberg integral approach to L-factors and then Shahidi's method of constructing L-functions by relating them to intertwining operators, leading to the definition of the the L-factors of tempered non degenerate representations. The lecture closes with a discussion of L-factors for nontempered representations.

#### Colloquium

16:30-17:30 Room #123 (Graduate School of Math. Sci. Bldg.)

Analysis of the Navier-Stokes and Complex Fluids Flow (ENGLISH)

**Matthias Hieber**(TU Darmstadt, Germany)Analysis of the Navier-Stokes and Complex Fluids Flow (ENGLISH)

[ Abstract ]

In this talk, we discuss the dynamics of fluid flow generated by the Navier-Stokes equations or, more generally, by models describing complex fluid flows. Besides classical questions concerning well-posedness of the underlying equations, we investigate analytically models arising in the theory of free boundary value problems, viscoelastic fluids and liquid crystals.

In this talk, we discuss the dynamics of fluid flow generated by the Navier-Stokes equations or, more generally, by models describing complex fluid flows. Besides classical questions concerning well-posedness of the underlying equations, we investigate analytically models arising in the theory of free boundary value problems, viscoelastic fluids and liquid crystals.

### 2013/07/25

#### thesis presentations

15:00-16:15 Room #122 (Graduate School of Math. Sci. Bldg.)

Discrete integrable equations over finite fields(有限体上の離散可積分方程式) (JAPANESE)

**Masataka KANKI**(Guraduate School of Mathematical Sciences the University of Tokyo)Discrete integrable equations over finite fields(有限体上の離散可積分方程式) (JAPANESE)

#### Lectures

13:00-15:00 Room #126 (Graduate School of Math. Sci. Bldg.)

)

Quantum Chern-Simons field theory (ENGLISH)

**Joergen E Andersen**(Centre for Quantum Geometry of Moduli Spaces (QGM), Aarhus University, Denmark)

Quantum Chern-Simons field theory (ENGLISH)

### 2013/07/24

#### Number Theory Seminar

16:40-17:40 Room #056 (Graduate School of Math. Sci. Bldg.)

The determinant of a double covering of the projective space of even dimension and the discriminant of the branch locus (JAPANESE)

**Yasuhiro Terakado**(University of Tokyo)The determinant of a double covering of the projective space of even dimension and the discriminant of the branch locus (JAPANESE)

#### Operator Algebra Seminars

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

The sofic property for groups and dynamical systems (ENGLISH)

**Mikael Pichot**(McGill Univ.)The sofic property for groups and dynamical systems (ENGLISH)

### 2013/07/23

#### PDE Real Analysis Seminar

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

Analysis of the Simplified Ericksen-Leslie Model for Liquid Crystals (ENGLISH)

**Matthias Hieber**(Technische Universität Darmstadt)Analysis of the Simplified Ericksen-Leslie Model for Liquid Crystals (ENGLISH)

[ Abstract ]

Consider the Ericksen-Leslie model for the flow of liquid crystals in a bounded domain $\\Omega \\subset \\R^n$. In this talk we discuss various simplifications of the general model and describe a dynamic theory for the simplified equations by analyzing it as a quasilinear system. In particular, we show the existence of a unique, global, strong solutions to this system provided the initial data are close to an equilibrium or the solution is eventually bounded in the norm of the underlying state space. In this case the solution converges exponentially to an equilibrium. Moreover, the solution is shown to be real analytic, jointly in time and space.

We further analyze a non-isothermal extension of this model safisfying the first and second law of thermodynamics and show that results of the above type hold as well in this setting.

This is joint work with M. Nesensohn, J. Prüss and K. Schade.

Consider the Ericksen-Leslie model for the flow of liquid crystals in a bounded domain $\\Omega \\subset \\R^n$. In this talk we discuss various simplifications of the general model and describe a dynamic theory for the simplified equations by analyzing it as a quasilinear system. In particular, we show the existence of a unique, global, strong solutions to this system provided the initial data are close to an equilibrium or the solution is eventually bounded in the norm of the underlying state space. In this case the solution converges exponentially to an equilibrium. Moreover, the solution is shown to be real analytic, jointly in time and space.

We further analyze a non-isothermal extension of this model safisfying the first and second law of thermodynamics and show that results of the above type hold as well in this setting.

This is joint work with M. Nesensohn, J. Prüss and K. Schade.

#### Numerical Analysis Seminar

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

Boundary Integral Equation Method for several Laplace equations with crack(s) (JAPANESE)

[ Reference URL ]

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

**Akira Sasamoto**(National Institute of Advanced Industrial Science and Technology)Boundary Integral Equation Method for several Laplace equations with crack(s) (JAPANESE)

[ Reference URL ]

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

#### Lectures

13:00-15:00 Room #002 (Graduate School of Math. Sci. Bldg.)

)

Moduli space approach for protein structures (ENGLISH)

**Joergen E Andersen**(Centre for Quantum Geometry of Moduli Spaces (QGM), Aarhus University, Denmark)

Moduli space approach for protein structures (ENGLISH)

### 2013/07/22

#### thesis presentations

13:30-14:45 Room #128 (Graduate School of Math. Sci. Bldg.)

The Stokes semigroup on non-decaying spaces(非減衰空間上のストークス半群) (JAPANESE)

**Ken ABE**(Guraduate School of Mathematical Sciences the University of Tokyo)The Stokes semigroup on non-decaying spaces(非減衰空間上のストークス半群) (JAPANESE)

#### thesis presentations

15:30-16:45 Room #128 (Graduate School of Math. Sci. Bldg.)

A few topics related to maximum principles(最大値原理に関連する諸課題) (JAPANESE)

**Nao HAMAMUKI**(Guraduate School of Mathematical Sciences the University of Tokyo)A few topics related to maximum principles(最大値原理に関連する諸課題) (JAPANESE)

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