## Seminar information archive

### 2014/11/20

#### Operator Algebra Seminars

13:00-15:00   Room #128 (Graduate School of Math. Sci. Bldg.)
Reiji Tomatsu (Hokkaido University)
Introduction to Haagerup's bicentralizer paper (English)

#### Infinite Analysis Seminar Tokyo

15:00-18:30   Room #002 (Graduate School of Math. Sci. Bldg.)
Fumihiko Nomoto (Department of Mathematics, Tokyo Institute of Technology, Graduate school of science and Engineering) 15:00-16:30
An explicit formula for the specialization of nonsymmetric
Macdonald polynomials at $t = \infty$ (JAPANESE)
[ Abstract ]
Orr-Shimozono obtained an explicit formula for nonsymmetric Macdonald polynomials with Hecke parameter $t$ set to $\infty$, which is described in terms of an affine root system
and an affine Weyl group. On the basis of this work, we give another explicit formula for the specialization above, which is described in terms of the quantum Bruhat graph associated with a finite root system and a finite Weyl group.
More precisely, we interpret the specialization above as the graded character of an explicitly specified set of quantum Lakshmibai-Seshadri (LS) paths. Here we note that the set of quantum LS paths (of a given shape) provides an explicit realization of the crystal basis of a quantum Weyl module over the quantum affine algebra.
In this talk, I will explain our explicit formula
by exhibiting a few examples.
Also, I will give an outline of the proof.
Masanori Ando (Wakkanai Hokusei Gakuen University) 17:00-18:30
divisor function and strict partition (JAPANESE)
[ Abstract ]
We know that the q-series identity of Uchimura-type is related with the divisor function.
It is obtained also as a specialization of basic hypergeometric series.
In this seminar, we interprete this identity from the point of view of combinatorics of partitions of integers.
We give its proof by using the mock involution map.

### 2014/11/19

#### Operator Algebra Seminars

13:00-15:00   Room #126 (Graduate School of Math. Sci. Bldg.)
Reiji Tomatsu (Hokkaido University)
Introduction to Haagerup's bicentralizer paper (English)

#### Number Theory Seminar

16:40-17:40   Room #056 (Graduate School of Math. Sci. Bldg.)
Fabien Pazuki (Univ Bordeaux and Univ Copenhagen)
Bad reduction of curves with CM jacobians (English)
[ Abstract ]
An abelian variety defined over a number field and having complex multiplication (CM) has potentially good reduction everywhere. If a curve of positive genus which is defined over a number field has good reduction at a given finite place, then so does its jacobian variety. However, the converse statement is false already in the genus 2 case, as can be seen in the entry $[I_0-I_0-m]$ in Namikawa and Ueno's classification table of fibres in pencils of curves of genus 2. In this joint work with Philipp Habegger, our main result states that this phenomenon prevails for certain families of curves.

We prove the following result: Let F be a real quadratic number field. Up to isomorphisms there are only finitely many curves C of genus 2 defined over $\overline{\mathbb{Q}}$ with good reduction everywhere and such that the jacobian Jac(C) has CM by the maximal order of a quartic, cyclic, totally imaginary number field containing F. Hence such a curve will almost always have stable bad reduction at some prime whereas its jacobian has good reduction everywhere. A remark is that one can exhibit an infinite family of genus 2 curves with CM jacobian such that the endomorphism ring is the ring of algebraic integers in a cyclic extension of $\mathbb{Q}$ of degree 4 that contains $\mathbb{Q}(\sqrt{5})$, for example.

#### Mathematical Biology Seminar

14:50-16:20   Room #122 (Graduate School of Math. Sci. Bldg.)
Joe Yuichiro Wakano (Department of Mathematical Sciences Based on Modeling and Analysis)
Introduction of Adaptive Dynamics and its application to finite population (JAPANESE)
[ Abstract ]

Replicator-Mutator方程式系（積分微分方程式系）によって定式化し、
そこから得られるモーメントの時間発展方程式（ODE）に揺らぎの項を

[ Reference URL ]
http://joefs.mind.meiji.ac.jp/~joe/

### 2014/11/18

#### Tuesday Seminar on Topology

16:30-18:00   Room #056 (Graduate School of Math. Sci. Bldg.)
Charles Siegel (Kavli IPMU)
A Modular Operad of Embedded Curves (ENGLISH)
[ Abstract ]
Modular operads were introduced by Getzler and Kapranov to formalize the structure of gluing maps between moduli of stable marked curves. We present a construction of analogous gluing maps between moduli of pluri-log-canonically embedded marked curves, which fit together to give a modular operad of embedded curves. This is joint work with Satoshi Kondo and Jesse Wolfson.

#### Operator Algebra Seminars

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

### 2014/11/12

#### Number Theory Seminar

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

### 2014/11/11

#### Tuesday Seminar on Topology

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

#### Seminar on Probability and Statistics

16:30-17:40   Room #052 (Graduate School of Math. Sci. Bldg.)
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.)
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 ]
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.)
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 $C^n$.

#### Classical Analysis

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

### 2014/11/07

#### Geometry Colloquium

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

### 2014/11/05

#### Operator Algebra Seminars

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

### 2014/11/04

#### Tuesday Seminar on Topology

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

#### Seminar on Probability and Statistics

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

#### Classical Analysis

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

### 2014/10/28

#### Number Theory Seminar

16:40-18:50   Room #002 (Graduate School of Math. Sci. Bldg.)
Judith Ludwig (Imperial college) 16:40-17:40