## Seminar information archive

Seminar information archive ～09/14｜Today's seminar 09/15 | Future seminars 09/16～

#### Operator Algebra Seminars

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

Introduction to Haagerup's bicentralizer paper (ENGLISH)

**Reiji Tomatsu**(Hokkaido University)Introduction to Haagerup's bicentralizer paper (ENGLISH)

### 2014/11/17

#### Seminar on Geometric Complex Analysis

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

On strong K-stability of polarized algebraic manifolds (JAPANESE)

**Yasufumi Nitta**(Tokyo Institute of Technology)On strong K-stability of polarized algebraic manifolds (JAPANESE)

#### Operator Algebra Seminars

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

Introduction to Haagerup's bicentralizer paper (English)

**Reiji Tomatsu**(Hokkaido University)Introduction to Haagerup's bicentralizer paper (English)

### 2014/11/14

#### Geometry Colloquium

10:00-11:30 Room #126 (Graduate School of Math. Sci. Bldg.)

Symplectic displacement energy for exact Lagrangian immersions

(JAPANESE)

**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.

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.

### 2014/11/12

#### Number Theory Seminar

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

Relative (φ, Γ)-modules (English)

**Ruochuan Liu**(BICMR)Relative (φ, Γ)-modules (English)

[ Abstract ]

In this talk, we will introduce the theory of (φ, Γ)-modules for general adic spaces. This is a joint work with Kedlaya.

In this talk, we will introduce the theory of (φ, Γ)-modules for general adic spaces. This is a joint work with Kedlaya.

### 2014/11/11

#### Tuesday Seminar on Topology

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

Unifying unexpected exceptional Dehn surgeries (ENGLISH)

**Kenneth Baker**(University of Miami)Unifying unexpected exceptional Dehn surgeries (ENGLISH)

[ Abstract ]

This past summer Dunfield-Hoffman-Licata produced examples of asymmetric, hyperbolic, 1-cusped 3-manifolds with pairs of lens space Dehn fillings through a search of the extended SnapPea census.

Examinations of these examples with Hoffman and Licata lead us to coincidences with other work in progress that gives a simple holistic topological approach towards producing and extending many of these families. In this talk we'll explicitly describe our construction and discuss related applications of the technique.

This past summer Dunfield-Hoffman-Licata produced examples of asymmetric, hyperbolic, 1-cusped 3-manifolds with pairs of lens space Dehn fillings through a search of the extended SnapPea census.

Examinations of these examples with Hoffman and Licata lead us to coincidences with other work in progress that gives a simple holistic topological approach towards producing and extending many of these families. In this talk we'll explicitly describe our construction and discuss related applications of the technique.

#### Seminar on Probability and Statistics

16:30-17:40 Room #052 (Graduate School of Math. Sci. Bldg.)

Local Ordinal Embedding

**Terada, Yoshikazu**(CiNet / Center for Information and Neural Networks)Local Ordinal Embedding

### 2014/11/10

#### FMSP Lectures

17:00-18:00 Room #128 (Graduate School of Math. Sci. Bldg.)

Discrete Painlevé equations with periodic coefficients (ENGLISH)

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

**Alfred Ramani**(Ecole Polytechnique)Discrete Painlevé equations with periodic coefficients (ENGLISH)

[ Abstract ]

We present a series of results on discrete Painlevé equations with coefficients which are periodic functions of the independent variable. We show by explicit construction that for each affine Weyl group there exists an equation the coefficients of which have maximal periodicity. New results on equations associated to the affine Weyl group E_8 are also presented.

[ Reference URL ]We present a series of results on discrete Painlevé equations with coefficients which are periodic functions of the independent variable. We show by explicit construction that for each affine Weyl group there exists an equation the coefficients of which have maximal periodicity. New results on equations associated to the affine Weyl group E_8 are also presented.

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

#### Seminar on Geometric Complex Analysis

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

On a convex level set of a plurisubharmonic function and the support of the Monge-Ampere current (JAPANESE)

**Yusaku Tiba**(Tokyo Institute of Technology)On a convex level set of a plurisubharmonic function and the support of the Monge-Ampere current (JAPANESE)

[ Abstract ]

In this talk, we study a geometric property of a continuous plurisubharmonic function which is a solution of the Monge-Ampere equation and has a convex level set. By using our results and Lempert's results, we show a relation between the supports of the Monge-Ampere currents and complex $k$-extreme points of closed balls for the Kobayashi distance in a bounded convex domain in $C^n$.

In this talk, we study a geometric property of a continuous plurisubharmonic function which is a solution of the Monge-Ampere equation and has a convex level set. By using our results and Lempert's results, we show a relation between the supports of the Monge-Ampere currents and complex $k$-extreme points of closed balls for the Kobayashi distance in a bounded convex domain in $C^n$.

#### Classical Analysis

16:00-17:00 Room #122 (Graduate School of Math. Sci. Bldg.)

DIFFERENTIAL GALOIS THEORY AND INTEGRABILITY OF DYNAMICAL SYSTEMS

**Jean-Pierre RAMIS**(Toulouse)DIFFERENTIAL GALOIS THEORY AND INTEGRABILITY OF DYNAMICAL SYSTEMS

[ Abstract ]

We will explain how to get obstructions to the integrability of analytic Hamiltonian Systems (in the classical Liouville sense) using Differential Galois Theory (introduced by Emile Picard at the end of XIX-th century). It is the so-called Morales-Ramis theory. Even if this sounds abstract, there exist efficient algorithms allowing to apply the theory and a lot of applications in various domains.

Firstly I will present basics on Hamiltonian Systems and integrability on one side and on Differential Galois Theory on the other side. Then I will state the main theorems. Afterwards I will describe some applications.

We will explain how to get obstructions to the integrability of analytic Hamiltonian Systems (in the classical Liouville sense) using Differential Galois Theory (introduced by Emile Picard at the end of XIX-th century). It is the so-called Morales-Ramis theory. Even if this sounds abstract, there exist efficient algorithms allowing to apply the theory and a lot of applications in various domains.

Firstly I will present basics on Hamiltonian Systems and integrability on one side and on Differential Galois Theory on the other side. Then I will state the main theorems. Afterwards I will describe some applications.

### 2014/11/07

#### Geometry Colloquium

10:00-11:30 Room #126 (Graduate School of Math. Sci. Bldg.)

Harmonic maps into the hyperbolic plane and their applications to surface theory (Japanese)

**Shinpei KOBAYASHI**(Hokkaido University)Harmonic maps into the hyperbolic plane and their applications to surface theory (Japanese)

[ Abstract ]

Harmonic maps from two-dimensional Riemannian manifolds into the hyperbolic plane have been well studied. Since constant mean curvature surfaces in the Minkowski space have harmonic Gauss maps into the hyperbolic plane, there exist applications to surface theory.

In 1998, Dorfmeister, Pedit and Wu established the construction method of harmonic maps into symmetric spaces via loop group method. Recently, harmonic maps into the hyperbolic plane appear in various classes of surfaces, e.g., minimal surfaces in the Heisenberg group,

maximal surfaces in the anti-de Sitter space or constant Gaussian curvature surfaces in the hyperbolic space. In this talk I will talk about the general construction method of harmonic maps from surfaces into symmetric spaces via loop group method and the case of the hyperbolic plane in details.

Harmonic maps from two-dimensional Riemannian manifolds into the hyperbolic plane have been well studied. Since constant mean curvature surfaces in the Minkowski space have harmonic Gauss maps into the hyperbolic plane, there exist applications to surface theory.

In 1998, Dorfmeister, Pedit and Wu established the construction method of harmonic maps into symmetric spaces via loop group method. Recently, harmonic maps into the hyperbolic plane appear in various classes of surfaces, e.g., minimal surfaces in the Heisenberg group,

maximal surfaces in the anti-de Sitter space or constant Gaussian curvature surfaces in the hyperbolic space. In this talk I will talk about the general construction method of harmonic maps from surfaces into symmetric spaces via loop group method and the case of the hyperbolic plane in details.

### 2014/11/05

#### Operator Algebra Seminars

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

On the noncommutativity of the central sequence $C^*$-algebra $F(A)$ (ENGLISH)

**Hiroshi Ando**(Univ. Copenhagen)On the noncommutativity of the central sequence $C^*$-algebra $F(A)$ (ENGLISH)

#### Mathematical Biology Seminar

14:50-16:20 Room #122 (Graduate School of Math. Sci. Bldg.)

Ecological conditions favoring budding in colonial organisms under environmental disturbance (JAPANESE)

[ Reference URL ]

https://sites.google.com/site/mayukonakamarulab/

**Mayuko Nakamaru**(Department of Value and Decision Science, Tokyo Institute of Technology)Ecological conditions favoring budding in colonial organisms under environmental disturbance (JAPANESE)

[ Reference URL ]

https://sites.google.com/site/mayukonakamarulab/

### 2014/11/04

#### Tuesday Seminar on Topology

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

The coarse geometry of Teichmuller space. (ENGLISH)

**Brian Bowditch**(University of Warwick)The coarse geometry of Teichmuller space. (ENGLISH)

[ Abstract ]

We describe some results regarding the coarse geometry of the

Teichmuller space

of a compact surface. In particular, we describe when the Teichmuller

space admits quasi-isometric embeddings of euclidean spaces and

half-spaces.

We also give some partial results regarding the quasi-isometric rigidity

of Teichmuller space. These results are based on the fact that Teichmuller

space admits a ternary operation, natural up to bounded distance

which endows it with the structure of a coarse median space.

We describe some results regarding the coarse geometry of the

Teichmuller space

of a compact surface. In particular, we describe when the Teichmuller

space admits quasi-isometric embeddings of euclidean spaces and

half-spaces.

We also give some partial results regarding the quasi-isometric rigidity

of Teichmuller space. These results are based on the fact that Teichmuller

space admits a ternary operation, natural up to bounded distance

which endows it with the structure of a coarse median space.

#### Seminar on Probability and Statistics

16:30-17:40 Room #052 (Graduate School of Math. Sci. Bldg.)

Conditions for consistency of a log-likelihood-based information criterion in normal multivariate linear regression models under the violation of normality assumption

**YANAGIHARA, Hirokazu**(Graduate School of Science, Hiroshima University)Conditions for consistency of a log-likelihood-based information criterion in normal multivariate linear regression models under the violation of normality assumption

### 2014/10/29

#### Operator Algebra Seminars

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

The classification of easy quantum groups (ENGLISH)

**Sven Raum**(RIMS, Kyoto Univ.)The classification of easy quantum groups (ENGLISH)

#### Lie Groups and Representation Theory

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

Harmonic analysis on reductive p-adic symmetric spaces. (ENGLISH)

**Patrick Delorme**(UER Scientifique de Luminy Universite d'Aix-Marseille II )Harmonic analysis on reductive p-adic symmetric spaces. (ENGLISH)

[ Abstract ]

In this lecture we will review the Plancherel formula that

we got by looking to neighborhoods at infinity of the

symmetric spaces and then using the method of Sakellaridis-Venkatesh

for spherical varieties for a split group. For us the group

is not necessarily split. We will try to show what questions

are raised by this work for real spherical varieties.

We will present in the last part a joint work with Pascale

Harinck and Yiannis Sakellaridis in which we prove Paley-Wiener

theorems for symmetric spaces.

In this lecture we will review the Plancherel formula that

we got by looking to neighborhoods at infinity of the

symmetric spaces and then using the method of Sakellaridis-Venkatesh

for spherical varieties for a split group. For us the group

is not necessarily split. We will try to show what questions

are raised by this work for real spherical varieties.

We will present in the last part a joint work with Pascale

Harinck and Yiannis Sakellaridis in which we prove Paley-Wiener

theorems for symmetric spaces.

#### Classical Analysis

16:00-17:00 Room #117 (Graduate School of Math. Sci. Bldg.)

Whittaker functions and Barnes-Type Lemmas (ENGLISH)

**Eric Stade**(University of Colorado Boulder)Whittaker functions and Barnes-Type Lemmas (ENGLISH)

[ Abstract ]

In the theory of automorphic forms on GL(n,R), which concerns harmonic analysis and representation theory of this group, certain special functions known as GL(n,R) Whittaker functions play an important role. These Whittaker functions are generalizations of classical Whittaker (or, more specifically, Bessel) functions.

Mellin transforms of products of GL(n,R) Whittaker functions may be expressed as certain Barnes type integrals, or equivalently, as hypergeometric series of unit argument. The general theory of automorphic forms predicts that these Mellin transforms reduce, in certain cases, to products of gamma functions. That this does in fact occur amounts to a whole family of generalizations of the so-called Barnes' Lemma and Barnes' Second Lemma, from the theory of hypergeometric series. We will explore these generalizations in this talk.

This talk will not require any specific knowledge of automorphic forms.

In the theory of automorphic forms on GL(n,R), which concerns harmonic analysis and representation theory of this group, certain special functions known as GL(n,R) Whittaker functions play an important role. These Whittaker functions are generalizations of classical Whittaker (or, more specifically, Bessel) functions.

Mellin transforms of products of GL(n,R) Whittaker functions may be expressed as certain Barnes type integrals, or equivalently, as hypergeometric series of unit argument. The general theory of automorphic forms predicts that these Mellin transforms reduce, in certain cases, to products of gamma functions. That this does in fact occur amounts to a whole family of generalizations of the so-called Barnes' Lemma and Barnes' Second Lemma, from the theory of hypergeometric series. We will explore these generalizations in this talk.

This talk will not require any specific knowledge of automorphic forms.

### 2014/10/28

#### Number Theory Seminar

16:40-18:50 Room #002 (Graduate School of Math. Sci. Bldg.)

A p-adic Labesse-Langlands transfer (English)

Plectic cohomology (English)

**Judith Ludwig**(Imperial college) 16:40-17:40A p-adic Labesse-Langlands transfer (English)

[ Abstract ]

Let B be a definite quaternion algebra over the rationals, G the algebraic group defined by the units in B and H the subgroup of G of norm one elements. Then the classical transfer of automorphic representations from G to H is well understood thanks to Labesse and Langlands, who proved formulas for the multiplicity of irreducible admissible representations of H(adeles) in the discrete automorphic spectrum.

The goal of this talk is to prove a p-adic version of this transfer. By this we mean an extension of the classical transfer to p-adic families of automorphic forms as parametrized by certain rigid analytic spaces called eigenvarieties. We will prove the p-adic transfer by constructing a morphism between eigenvarieties, which agrees with the classical transfer on points corresponding to classical automorphic representations.

Let B be a definite quaternion algebra over the rationals, G the algebraic group defined by the units in B and H the subgroup of G of norm one elements. Then the classical transfer of automorphic representations from G to H is well understood thanks to Labesse and Langlands, who proved formulas for the multiplicity of irreducible admissible representations of H(adeles) in the discrete automorphic spectrum.

The goal of this talk is to prove a p-adic version of this transfer. By this we mean an extension of the classical transfer to p-adic families of automorphic forms as parametrized by certain rigid analytic spaces called eigenvarieties. We will prove the p-adic transfer by constructing a morphism between eigenvarieties, which agrees with the classical transfer on points corresponding to classical automorphic representations.

**Jan Nekovar**(Université Paris 6) 17:50-18:50Plectic cohomology (English)

### 2014/10/27

#### Algebraic Geometry Seminar

14:50-16:20 Room #122 (Graduate School of Math. Sci. Bldg.)

On projective varieties with very large canonical volume (ENGLISH)

**Meng Chen**(Fudan University)On projective varieties with very large canonical volume (ENGLISH)

[ Abstract ]

For any positive integer n>0, a theorem of Hacon-McKernan, Takayama and Tsuji says that there is a constant c(n) so that the m-canonical map is birational onto its image for all smooth projective n-folds and all m>=c(n). We are interested in the following problem "P(n)": is there a constant M(n) so that, for all smooth projective n-fold X with Vol(X)>M(n), the m-canonical map of X is birational for all m>=c(n-1). The answer to “P_n" is positive due to Bombieri when $n=2$ and to Todorov when $n=3$. The aim of this talk is to introduce my joint work with Zhi Jiang from Universite Paris-Sud. We give a positive answer in dimensions 4 and 5.

For any positive integer n>0, a theorem of Hacon-McKernan, Takayama and Tsuji says that there is a constant c(n) so that the m-canonical map is birational onto its image for all smooth projective n-folds and all m>=c(n). We are interested in the following problem "P(n)": is there a constant M(n) so that, for all smooth projective n-fold X with Vol(X)>M(n), the m-canonical map of X is birational for all m>=c(n-1). The answer to “P_n" is positive due to Bombieri when $n=2$ and to Todorov when $n=3$. The aim of this talk is to introduce my joint work with Zhi Jiang from Universite Paris-Sud. We give a positive answer in dimensions 4 and 5.

#### Seminar on Geometric Complex Analysis

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

On the minimality of canonically attached singular Hermitian metrics on certain nef line bundles (JAPANESE)

**Takayuki Koike**(University of Tokyo)On the minimality of canonically attached singular Hermitian metrics on certain nef line bundles (JAPANESE)

[ Abstract ]

We apply Ueda theory to a study of singular Hermitian metrics of a (strictly) nef line bundle $L$. Especially we study minimal singular metrics of $L$, metrics of $L$ with the mildest singularities among singular Hermitian metrics of $L$ whose local weights are plurisubharmonic. In some situations, we determine a minimal singular metric of $L$. As an application, we give new examples of (strictly) nef line bundles which admit no smooth Hermitian metric with semi-positive curvature.

We apply Ueda theory to a study of singular Hermitian metrics of a (strictly) nef line bundle $L$. Especially we study minimal singular metrics of $L$, metrics of $L$ with the mildest singularities among singular Hermitian metrics of $L$ whose local weights are plurisubharmonic. In some situations, we determine a minimal singular metric of $L$. As an application, we give new examples of (strictly) nef line bundles which admit no smooth Hermitian metric with semi-positive curvature.

### 2014/10/25

#### Harmonic Analysis Komaba Seminar

13:30-16:30 Room #128 (Graduate School of Math. Sci. Bldg.)

Approximation in Banach space by linear positive operators (JAPANESE)

Local ill-posedness of the Euler equations in a critical Besov space (JAPANESE)

**Yoshihiro Sawano**(Tokyo Metropolitan University) 13:30-14:30Approximation in Banach space by linear positive operators (JAPANESE)

[ Abstract ]

We obtain a sufficient condition for the

convergence of positive linear operators in Banach

function spaces on Rn and derive a Korovkin type

theorem for these spaces. Also, we generalized

this result via statistical sense. This is a joint

work with Professor Arash Ghorbanalizadeh.

We obtain a sufficient condition for the

convergence of positive linear operators in Banach

function spaces on Rn and derive a Korovkin type

theorem for these spaces. Also, we generalized

this result via statistical sense. This is a joint

work with Professor Arash Ghorbanalizadeh.

**Tsuyoshi Yoneda**(Tokyo Institute of Technology) 15:00-16:30Local ill-posedness of the Euler equations in a critical Besov space (JAPANESE)

### 2014/10/22

#### Operator Algebra Seminars

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

Free independence in ultraproduct von Neumann algebras and applications (ENGLISH)

**Yusuke Isono**(Kyoto Univ.)Free independence in ultraproduct von Neumann algebras and applications (ENGLISH)

#### Mathematical Biology Seminar

14:50-16:20 Room #122 (Graduate School of Math. Sci. Bldg.)

Fast reaction limit of a system with different reaction terms (JAPANESE)

**Harunori Monobe**(Meiji Institute for Advanced Study of Mathematical Sciences)Fast reaction limit of a system with different reaction terms (JAPANESE)

### 2014/10/21

#### Tuesday Seminar on Topology

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

Vanishing theorems for p-local homology of Coxeter groups and their alternating subgroups (JAPANESE)

**Toshiyuki Akita**(Hokkaido University)Vanishing theorems for p-local homology of Coxeter groups and their alternating subgroups (JAPANESE)

[ Abstract ]

Given a prime number $p$, we estimate vanishing ranges of $p$-local homology groups of Coxeter groups (of possibly infinite order) and alternating subgroups of finite reflection groups. Our results generalize those by Nakaoka for symmetric groups and Kleshchev-Nakano and Burichenko for alternating groups. The key ingredient is the equivariant homology of Coxeter complexes.

Given a prime number $p$, we estimate vanishing ranges of $p$-local homology groups of Coxeter groups (of possibly infinite order) and alternating subgroups of finite reflection groups. Our results generalize those by Nakaoka for symmetric groups and Kleshchev-Nakano and Burichenko for alternating groups. The key ingredient is the equivariant homology of Coxeter complexes.

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