Japanese | English

# Kobe Studio Seminar for Mathematics

## Schedule of studies and past topics:

### Past studies

date:
2017/12/01 13:00-15:00
room:
A739
title:
Dirichlet fundamental regions and their properties
speaker:
Akira Ushijima (Kanazawa University)
abstract:

We survey results of Dirichlet fundamental regions for Fuchsian groups. The talk will be begun with recalling definitions necessary for introducing Dirichlet fundamental regions, followed by their basic facts, including the denseness of generic Dirichlet fundamental regions by Beardon, and related results by Näätänen and Fera.

date:
2017/10/27 13:00-15:00
room:
A739
title:
Various models of hyperbolic space and hyperbolic geometry
speaker:
Akira Ushijima (Kanazawa University)
abstract:

Since hyperbolic space does not hold the parallel postulate, it is impossible to embed it into Euclidean space of the same dimension "completely". A model of hyperbolic space is a way to embed it into Euclidean space so that some of the properties of hyperbolic geometry are not compatible with those of Euclidean geometry. We survey some of the models and their relations, together with basic facts on hyperbolic geometry.

date:
2017/01/23 13:00-
room:
A746
title:
Report on Low Dimensional Topology and Computer Graphics
moderator:
Mikami Hirasawa (Nagoya Institute of Technology)
speaker:
Yusuke Kiriu (Studio Phones)
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2016/12/11 13:00-15:00
room:
A739
title:
On generic Dirichlet fundamental polyhedra for low-dimensional hyperbolic manifolds
speaker:
Akira Ushijima (Kanazawa University)
abstract:

A Dirichlet fundamental polyhedron for a hyperbolic manifold is defined as the Voronoi diagram for the orbit of a point, called center in what follows, by the action of the fundamental group on the universal cover. Such a polyhedron is said to be generic if its combinatorial structure is stable under any perturbation of the center. Known results for such polyhedra, including its denseness of the set of centers corresponding to generic ones for hyperbolic surfaces, together with open questions are discussed in this talk.

date:
2016/03/04 13:00-
room:
A746
topic:
Theory of Operator Algebras
moderator:
Hiroyasu Hamada (National Institute of Technology, Sasebo College)
note:
This discussion is co-organized with KSS for Studies with Renderman.
date:
2016/01/23 13:00-
room:
Room at Nagoya Institute of Technology
title:
Report on Low Dimensional Topology and Computer Graphics
moderator:
Mikami Hirasawa (Nagoya Institute of Technology)
speaker:
Yusuke Kiriu (Studio Phones)
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2016/01/08 10:30-
room:
Room at Studio Phones (changed from A746)
topic:
Vertex operator algebra
moderator:
Yusuke Arike (University of Tsukuba)
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2016/01/09 10:30-
room:
Room at Studio Phones (changed from A746)
topic:
Vertex operator algebra
moderator:
Yusuke Arike (University of Tsukuba)
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2015/11/25 13:00-17:00
room:
A739
title:
Construction of Jacobi forms and its application to the flat invariants
speaker:
Ikuo Satake (Kagawa Univeristy)
abstract:

As a generalization of the Weyl group and its invariants theory, we study the elliptic Weyl group and its invariants. We have 3 kinds of invariants: the characters of the affine Lie algebras, the flat invariants (which corresponds to the Frobenius str.) for the elliptic root systems and the Jacobi forms for the root systems.

In this talk, we first give a construction of Jacobi forms for the root systems by the characters of the affine Lie algebras. Then we apply it to the construction of flat invariants for the elliptic root systems. By this construction, we obtain that some of the flat invariants have Fourier expansions whose coefficients are integers.

date:
2015/11/26 10:00-
room:
A746
discussion:
We'd like to have discussions on definitions, questions (and so on) related to Prof. Satake's talk. If you are interested in these discussions, please contact to the corresponding organizer: Kosaku Nagasaka in advance.
moderator:
Yusuke Kiriu (Studio Phones)
date:
2015/11/18 16:10-
room:
A739
title:
Discrete model of dynamics of vortex filament based on discrete integrable systems
speaker:
Kenji Kajiwara (IMI, Kyushu University)
abstract:

The local induction equation is well-known as a model of vortex filament in fluid dynamics. This describes a deformation of space curves in the binormal direction, and the complex curvature is governed by the nonlinear Schrödinger equation which is a typical integrable system. In this talk, starting from a brief introduction of discretization preserving integrability, we present a discrete model of dynamics of vortex filament based on this idea. The discrete complex curvature is governed by the discrete nonlinear Schrödinger equation (discrete in both space and time) proposed by Hirota-Tsujimoto. We discuss the relationship with the doubly discrete isotropic Heisenberg chain proposed by Hoffmann which is used for simulation of fluid flow in CG.

note:

This talk is co-organized with KSS for Studies with Renderman.

date:
2015/03/16 15:00-16:00
room:
A739
title:
C*-algebras generated by multiplication operators and composition operators
speaker:
Hiroyasu Hamada (National Institute of Technology, Sasebo College)
abstract:

1. Definition and examples of C*-algebras,
2. Definition and examples of composition operators, and
3. My research: C*-algebras generated by multiplication operators and composition operators.
date:
2015/02/24 13:00-14:50
room:
A739
title:
Evolution equations and variational principle
speaker:
Goro Akagi (Kobe University)
abstract:

Evolution Equations (EE for short) have been vigorously studied in views of mathematics as well as of physics ever since the notion of EE was introduced to describe the evolution of physical systems in an abstract fashion. In particular, the theory of EE has been applied to make a great contribution to explore the study of Partial Differential Equations. Moreover, in this field, Japanese mathematicians such as Kosaku Yosida, Toshio Kato, Yukio Komura established many pioneer works.

In this talk, the basic idea of EE will be explained, and then, the development of this field so far will be briefly surveyed (within the limits of time and speaker's ability). In the latter half, we shall review speaker's recent works, particularly on Variational Principle for EE with energy dissipation structures, to discuss some philosophical aspect, basic idea and results obtained so far. The latter half is based on a series of joint works with Ulisse Stefanelli (Vienna).

note:

This talk is co-organized with KSS for Studies with Renderman.

date:
2015/02/20 10:00-16:00
room:
A739
title:
Representation theory of tensor categories and its applications
speaker:
Kenichi Shimizu (Nagoya University)
abstract:

Given two representations of a group (or, more generally, a Hopf algebra), we can form their tensor product representation. This operation is associative and unital in a sense, and therefore we may say that the representations form a "monoid" with respect to the tensor product. The notion of a tensor category (or a monoidal category) is obtained by formalizing such a situation and is important in many areas of mathematics and mathematical physics as a framework to describe the theory.

By the way, studying representations of a given algebraic system is a common practice in algebra. The case of a tensor category is no exception, and its "representation theory" is a very interesting topic. I will overview the representation theory of tensor categories and talk about some applications to topology.

sessions:
10:00 - 11:00 "What is a tensor category?"

As a preparation, I recall the notion of a tensor category and overview related notions. I also give the formal definitions of a "representation" of a tensor category and "intertwiners" between them.

11:10 - 12:10 "Representation theory of a finite tensor category"

I outline the representation theory of finite tensor categories, which is a class of tensor categories introduced by Etingof and Ostrik. One of the important notions is an exact module category. I also recall their basic properties and, as an application, introduce the "Serre functor" on an exact module category.

13:30 - 14:30 "A categorical analogue of the modular function"

The modular function of a Hopf algebra is defined as an algebraic analogue of the modular function of a locally compact group. Etingof, Nikshych and Ostrik introduced a categorical analogue of the modular function based on the theory of exact module categories. I will explain their results from the viewpoint of the Serre functor.

15:00 - 16:00 "Unimodular finite tensor categories"

A locally compact group is said to be unimodular if its modular function is trivial. The unimodularity of a Hopf algebra and that of a finite tensor category are defined analogously. If time permits, I will talk about characterizations of unimodular finite tensor categories and their applications to topological invariants.

date:
2015/02/20 16:20-
room:
A739
discussion:

We'd like to have discussions on Dr. Shimizu's past studies in tensor categories.

moderator:
Yusuke Kiriu (Studio Phones)
date:
2015/02/19 16:00-17:30
room:
A739
title:
From the symplectic cohomology to the Hochschild cohomology of wrapped Fukaya category for punctured surfaces and more
speaker:
Masahiro Futaki (Kyoto University)
abstract:

In the seminal ICM talk in 1994 Kontsevich conjectured an isomorphism from the quantum cohomology to the Hochschild cohomology of the Fukaya category defined as a closed-open map in the context of mirror symmetry. This conjecture has been established in important cases (e.g. Abouzaid-Fukaya-Oh-Ohta-Ono for smooth compact toric manifolds).

Analogously open version of the conjecture for Liouville domains (exact symplectic manifold with contact type boundary) can be formulated by replacing the quantum cohomology with the symplectic cohomology and Fukaya category with the wrapped Fukaya category (e.g. Seidel in somewhat specific form).

I will explain how the open version is true in the easy example of punctured surfaces (based on the criterion by Ganatra and calculations by Abouzaid-Auroux-Efimov-Katzarkov-Orlov and Bocklandt) and then discuss the effect of contact boundary surgery, namely the boundary connected sum of two disc bundles of $T^\ast S^2$.

date:
2014/12/16 16:00-16:30
room:
A748
title:
Minimal surfaces and CG
speaker:
Shoichi Fujimori (Okayama Univeristy)
abstract:

In this talk we exhibit some examples of how computer graphics have contributed to the development of minimal surface theory.

note:

This talk is co-organized with KSS for Studies with Renderman.

date:
2014/12/16 16:40-17:25
room:
A748
title:
A construction for embedded triply periodic minimal surfaces
speaker:
Shoichi Fujimori (Okayama Univeristy)
abstract:

In this talk we introduce a construction method for embedded triply periodic minimal surfaces and give examples of them.

date:
2014/12/16 17:30-18:00
room:
A748
discussion:

We'd like to have discussions on Prof. Fujimori's past studies in minimal surfaces and CG. Please visit the following link if you'd like to survey the topic after the seminar.

moderator:
Yusuke Kiriu (Studio Phones)
note:

This discussion is co-organized with KSS for Studies with Renderman.

date:
2014/10/17 15:40-16:40
room:
A739
title:
Isometric deformations of surfaces with singularities
speaker:
Kosuke Naokawa (Kobe University)
abstract:

A deformation of preserving the first fundamental form of a given surface is called an isometric deformation. In Euclidean 3-space, a deformation of rolling planar "paper" up into another surface such as a cylinder is a typical example of isometric deformations. In this talk, I explain isometric deformations of surfaces which have singularities of cross caps or cuspidal edges.

date:
2014/10/17 16:50-17:50
room:
A739
title:
An introduction to discrete differential geometry
speaker:
Masashi Yasumoto (Kobe University)
abstract:

In this talk, I will explain how to define Gaussian curvature and mean curvature for planar quadrilateral meshes in Euclidean 3-space, and if time permits, I will introduce several classes of discrete surfaces with special curvature conditions.

date:
2014/08/27 10:00-12:00, 13:30-15:00
room:
A746
discussion:

We'd like to have discussions on definitions, questions (and so on) related to Prof. Hirose's past studies in Mathematics and their computational methods. If you are interested in these discussions, please contact to the corresponding organizer: Kosaku Nagasaka in advance.

moderator:
Yusuke Kiriu (Studio Phones)
date:
2014/08/27 15:00-16:00, 16:20-17:20
room:
A739
title:
Recent applications of mathematics to computer graphics
speaker:
Sampei Hirose (Shibaura Institute of Technology)
abstract:
Please see the announcement of KSS for Studies with Renderman for further information.
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2014/08/28 11:00-12:00, TBA
room:
A746
discussion:

We'd like to have discussions on definitions, questions (and so on) related to Prof. Hirose's past studies in Mathematics and their computational methods. If you are interested in these discussions, please contact to the corresponding organizer: Kosaku Nagasaka in advance.

moderator:
Yusuke Kiriu (Studio Phones)
date:
2014/08/26 10:00-12:00, 13:30-15:00
room:
A746
discussion:

We'd like to have discussions on some possibilities to apply his methods to various algorithms (for or related to mathematical objects), definitions, questions (and so on) related to Prof. Yasui's past studies in Computer Sciences and their computational methods. If you are interested in these discussions, please contact to the corresponding organizer: Kosaku Nagasaka in advance.

moderator:
Yusuke Kiriu (Studio Phones)
date:
2014/08/26 15:00-16:00
room:
A739
title:
Fast computation of breadth-first search considering computer memory hierarchy
speaker:
Yuichiro Yasui (Kyushu University, IMI & JST CREST)
abstract:
Please see the announcement of KSS for Studies with Renderman for further information.
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2014/08/26 16:20-17:20
room:
A739
title:
Fast computation considering computer memory hierarchy for the computer graphics field
speaker:
Yuichiro Yasui (Kyushu University, IMI & JST CREST)
abstract:
Please see the announcement of KSS for Studies with Renderman for further information.
note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2014/05/23 15:10-16:10
room:
A739
title:
Visual Hyperbolic Geometry 1
speaker:
Yasushi Yamashita (Nara Women's University)
abstract:

We consider a simple class of Kleinian groups called once punctured torus groups. In this talk, we will show how to create a computer program from scratch that can visualize fundamental domain and limit sets of the groups. As an application, we will show the computer generated pictures of discreteness loci of several slices of SL(2,C)-character variety.

note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2014/05/23 16:20-17:20
room:
A739
title:
Visual Hyperbolic Geometry 2
speaker:
Yasushi Yamashita (Nara Women's University)
abstract:

We consider a simple class of Kleinian groups called once punctured torus groups. In this talk, we will show how to create a computer program from scratch that can visualize fundamental domain and limit sets of the groups. As an application, we will show the computer generated pictures of discreteness loci of several slices of SL(2,C)-character variety.

note:
This talk is co-organized with KSS for Studies with Renderman.
date:
2013/11/08 13:00-14:00
room:
A325
title:
Some results on derivations and higher derivations
speaker:
Hideo Kojima (Niigata University)
abstract:

Derivations and their kernels play an important role in Affine Algebraic Geometry and have been studied by many mathematicians. Recently, the kernels of higher derivations have been studied by several authors and some of the results on the kernels of derivations have been extended to the case of the kernels of higher derivations. In this talk, I first give a survey of some results on kernels of derivations. Then I give some results on kernels of higher derivations in polynomial rings.

date:
2013/11/08 14:20-15:20
room:
A325
title:
On Q-homology planes
speaker:
Hideo Kojima (Niigata University)
abstract:

A Q-homology is, by definition, a smooth complex affine surface with Betti numbers of the complex affine plane C^2. Some mathematicians have studied Q-homology planes since they are similar to C^2. In this talk, I give a survey of Q-homology planes.

date:
2013/11/08 16:00-17:00
room:
A325
title:
Galois points for a plane algebraic curve, and related topics
speaker:
Takeshi TAKAHASHI (Nagaoka National College of Technology)
abstract:

In 1996, Prof. Hisao Yoshihara (Niigata Univ.) defined "Galois point" for a plane algebraic curve, and has studied it. A Galois point is a point from which the projection induces a Galois extension of function fields. First I will explain the definition, Yoshihara's motivation and his results. Second I will talk on recent results related to Galois points.

date:
2013/10/09 16:40-
room:
A739
title:
The cd indices of CW posets --an approach from commutative algebra.
speaker:
Kohji Yanagawa (Kansai University)
abstract:

This is a joint work with Satoshi Murai (Yamaguchi University). The existence of the "cd index" is a mysterious phenomenon in enumeration problems of CW spheres (and more general combinatorial objects).

Except the existence itself, the strongest result on this notion must be its non-negativity given by K. Karu. Recently, we have reconstructed his proof from a view of commutative algebra, and gave new results. This talk is an introduction to the general theory of the cd index and our new method.

date:
2013/07/10 16:40-17:40
room:
A739
title:
Introduction to Morse functions and their Reeb graphs
speaker:
Osamu Saeki (Kyushu University)
abstract:

This is an introductory talk about Morse functions on manifolds, especially for non-specialists. Our main aim is to explain the so-called Reeb graphs associated to Morse functions, and how they are used to visualize a given function. If time permits, we will mention its generalization to differentiable maps into higher dimensional Euclidean spaces.

date:
2013/07/10 17:50-18:50
room:
A739
title:
On Math-for-Industry activities
speaker:
Osamu Saeki (Kyushu University)
abstract:

Some examples of the activities of the Institute of Mathematics for Industry, Kyushu University, will be presented. Meanwhile, the speaker will try to explain some important aspects of Mathematical researches related to industry, including his personal experiences and impressions. This talk will be basically informal.

date:
2013/06/22 15:00-16:30
room:
A739
title:
Orientable surfaces in space whose boundary is knotted.
speaker:
Mikami Hirasawa (Nagoya Institute of Technology)
abstract:

Consider orientable surfaces in space. When they have boundary, it is interesting when the boundary has a knot. On the other hand, it is known that every knotted circle in space has an orientable surface whose boundary coincides with the knot. In this talk, we show how to deal with such surfaces on the blackboard.

date:
2013/06/11 16:50-18:20
room:
A739
title:
On the generalization of the Fox coloring using quandles
speaker:
Ayumu Inoue (Aichi University of Education)
abstract:

The Fox coloring [Fox] for a knot diagram is simple but useful to classifying knots. If given two knot diagrams represent the same knot, the numbers of all Fox colorings for the diagrams coincide each other. Thus the number of all Fox coloring of a knot diagram gives rise to an invariant of knots.

We can generalize the notion of Fox coloring utilizing quandles. A quandle is an algebraic system which is efficient to study knots. Every knot diagram allows to be colored by any quandles. As well as Fox coloring, the number of all colorings by a quandle gives rise to a knot invariant.

Any one variable Laurent polynomial ring module enables a special quandle structure. We call this an Alexander quandle. Fox coloring coincides with a coloring by a certain Alexander quandle.

The goal of this talk is to show that the number of colorings for a knot diagram by an Alexander quandle is completely determined by Alexander polynomials of the knot [Inoue]. We will start with an introduction of quandle theory.

• [Fox] R. H. Fox, "A quick trip through knot theory", 1962 Topology of 3-manifolds and related topics (Proc. The Univ. of Georgia Institute, 1961), Prentice-Hall, Englewood Cliffs, N.J., 1962, 120--167.
• [Inoue] A. Inoue, "Quandle homomorphisms of knot quandles to Alexander quandles", J. Knot Theory Ramifications 10 (2001), no. 6, 813--821.

### Studio Phones Seminar Archives

date:
2013/02/21 15:10 - 16:40
room:
A739
title:
Chinese Mathematics in Qin and Han periods
speaker:
Makoto Tamura(Osaka Sangyo University)
abstract:

Zhangjiashan Han bamboo book "Suanshu-shu" and Qin bamboo book "Shu" housed at Yuelu Academy are mathematical books in ancient China, whose texts and photographs were published several years ago.

Our procedure was to decipher again the letters from the photographs with the following investigation from mathematical and historical viewpoints. In this talk, the contents of two books will be introduced briefly and some issues will be compared with those of "The Nine Chapters on the Mathematical Art."

date:
2012/09/27 1600-1800
room:
A750
title:
Heegaard splitting of distance exactly $n$ for each non-negative integer $n$
speaker:
Tsuyoshi Kobayashi (Nara Women's University) (joint work with Ayako Ido and Yeonhee Jang)
abstract:

Hempel introduced the concept of distance of Heegaard splitting by using curve complex, and showed that there exist Heegaard splittings of closed orientable 3-manifolds with distance $>n$ for any integer $n$. In this talk, we construct pairs of curves with distance exactly $n$ for any integer $n$, and we show that there exist Heegaard splittings of 3-manifolds with distance exactly $n$.

date:
2012/07/16 1000-1100
room:
A739
title:
Dimensions of triangulated categories with respect to subcategories
speaker:
Tokuji Araya(Tokuyama College of Technology)
abstract:

We will introduce the concept of the dimension of a triangulated category with respect to a fixed full subcategory. For the bounded derived category of an abelian category, upper bounds of the dimension with respect to a contravariantly finite subcategory and a resolving subcategory are given. Our methods not only recover some known results on the dimensions of derived categories in the sense of Rouquier, but also apply to various commutative and non-commutative noetherian rings.

date:
2012/07/16 1110-1210
room:
A739
title:
Bar-Natan's cobordism category of Khovanov-Rozansky homology
speaker:
Yasuyoshi Yonezawa(Nagoya University)
abstract:

Khovanov defined a bi-graded link homology whose Euler characteristic is Jones polynomial. Subsequently, Bar-Natan defined a cobordism category associated to Khovanov homology and showed a chain complex of cobordisms is a link invariant up to homotopy equivalence. In this talk, I'll introduce a cobordism category associated to Khovanov-Rozansky homology (a triple graded homology whose Euler characteristic is a specialized HOMFLY polynomial). If I have a time, I'll explain a relation of the cobordism category, a homotopy category of matrix factorizations and a category of Soergel bimodules.

date:
2012/07/16 1320-1430
room:
A739
title:
Silting mutation in triangulated categories
speaker:
Osamu Iyama(Nagoya University)
abstract:

Silting objects appeared in work of Keller-Vossieck on quiver representations. Following I.-Aihara (JLMS 2012), Koenig-Yang (arXiv:1203.5657) and Adachi-I.-Reiten, I will explain mutation theory of silting objects in triangulated categories as well as their relationship with t-structures and co-t-structures.

date:
2012/07/16 1450-1600
room:
A739
title:
Selfinjective quivers with potentials and derived equivalences
speaker:
Yuya Mizuno(Nagoya University)
abstract:

It is known that there is only trivial tilting module over selfinjective algebra. Hence it is difficult to give a derived equivalent algebra explicitly for selfinjective algebra. In this talk, I will explain some connections between selfinjective quivers with potentials and derived equivalences, and provide a derived equivalence class algebras.

date:
2012/07/16 1620-1730
room:
A739
title:
Derived Categories and Stability Conditions in Arithmetic Geometry
speaker:
Hiroki Minamide(Kobe University)
abstract:

I will start with a survay of well known properties of derived categories in algebraic geometry and Bridgeland's stability conditions. I also explain a Huybrechts' excellent article (arXiv:1009.4371). If we have enough time, I shall refer to relations with structures of Chow groups and some categorical problems in arithmetic geometry.

date:
2012/06/12 1300-1500
room:
A752
title:
Top cell attaching map in 3-cell complex
speaker:
Toshiyuki Miyauchi(Fukuoka University)
abstract:

I. M. James introduce the characteristic of a CW-complex $S^q\cup e^n\cup e^{q+n}$. This is a relation between the homotopy class of the attaching map of $e^{q+n}$ and the ring structure of the singular cohomology. For a CW-complex $S^q\cup e^n\cup e^{q+n+k}$, we consider a relation between the homotopy class of the attaching map of $e^{q+n+k}$ and the ring structure of a generalized cohomology.

date:
2012/06/11 1300-1500
room:
B103
title:
Unstable homotopy group
speaker:
Toshiyuki Miyauchi(Fukuoka University)
abstract:

I will give a brief description of unstable homotopy groups of CW-complexes. Specially, for a CW-complex X and its subcomplex A, I will talk about methods of calculation of homotopy groups of X using by homotopy groups of A, relative homotopy groups of (X,A) and the CW-structure of the homotopy fiber of a pinching map A to a point in X.

articles and slides (license is CC-BY-NC):
Miyauchi20120611.pdf
date:
2012/06/06 1000-1200, 1400-1800
room:
A748
title:
Categoricity
speaker:
Kota Takeuchi (Tsukuba University)
abstract:

We first introduce logical structures and discuss basic properties. Then we prove that strongly minimal structures are uncountably categorical. Specific examples of this result are "Vector spaces with fixed base field are isomorphic if and only if they have the same dimension defined by the linear dependence." and "Algebraically closed fields with characteristic p are isomorphic if and only if they have the same dimension defined by the algebraic dependence." This fact is a very simple version of Morley's categoricity theorem which is one of the most important classical result in model theory.

date:
2012/05/16 1250-1400
room:
B103
title:
Local fields and its arithmetic Part 2.
speaker:
Kazuma Shimomoto(Kansai University)
abstract:

I will talk about an elementary proof of (local) Kronecker-Weber theorem. Other topics will include local class field theory and its applications.

reference:
• J.-P. Serre, Local fields, Springer
• J. Neukirch, Algebraic number theory, Springer
date:
2012/05/16 1430-1530
room:
B103
title:
Bridgeland's stability conditions and it's wall-crossing.
speaker:
Hiroki Minamide(Kobe University)
abstract:

In this talk we shall survey recent progress on the Bridgeland's stability conditions and it's wall-crossing. The material covered in this talk is based almost entirely on the two celebrated articles by T. Bridgeland. We shall treat special objects the bounded derived category of coherent sheaves on smooth projective curves and K3/abelian surfaces. If there is enough time, I will also explain some results on relations classical stability and Bridgeland's stability.

date:
2012/05/16 1540-1610
room:
B103
title:
Local Bertini theorem and the Iwasawa's main conjecture
speaker:
Kazuma Shimomoto(Kansai University)
abstract:

This is a report on joint work with T. Ochiai (Osaka University) on the relation between the characteristic ideal arising from Hida deformation and the 2-variable p-adic L-function.

date:
2012/02/23 1000-1130
room:
A739
title:
Cellular and stellar stratified spaces
speaker:
Dai Tamaki(shinshu University)
abstract:

The speaker recently introduced a generalization and a refinement of cell complexes, called cellular stratified spaces, which allow us to extend techniques used by combinatorialists to study posets and simplicial complexes to much more general structures such as topological categories. This talk is an exposition of cellular stratified spaces and related structures. We mainly focus on motivations and (possible) applications.

date:
2012/02/22 1600-1730
room:
A739
title:
Simplicial and cellular structures in algebraic topology
speaker:
Dai Tamaki(shinshu University)
abstract:

We review simplicial and cellular structures used in algebraic topology, such as simplicial complexes, cell complexes, simplicial sets, simplicial spaces, $\Delta$-sets, and cosimplicial spaces, from a historical perspective. Simplicial complexes played a fundamental role when Poincare tried to define homology. Cell complexes and CW complexes were introduced by Whitehead and form basic building blocks of classical algebraic topology. In modern algebraic topology, model categories equipped with simplicial or cellular structures are basic objects of study. Simplicial sets also provide a foundation of $(\infty,1)$-categories, from which Lurie developed derived algebraic geometry and extended topological quantum field theories. If time allows, we might be able to discuss these recent developments.

articles and slides (license is CC-BY-NC):
abstract_dai_tamaki.pdf
date:
2012/02/10 1000-1200, 1400-1800
place and room:
Studio Phones Room301B
title:
Higher-order generalization of Fukaya's Morse homotopy invariant of 3-manifolds
speaker:
abstract:

We give a higher order generalization of Fukaya's Morse homotopy theoretic approach to 2-loop Chern--Simons perturbation theory. In this talk, we construct a sequence of invariants of homology 3-spheres with values in a space of trivalent graphs (Jacobi diagrams) by using Morse homotopy theory.

date:
2012/02/09 1500-1600
room:
A739
title:
Morse theory and invariants of manifolds
speaker:
abstract:

The diffeomorphism type of a differentiable manifold can be studied by considering some smooth function on the manifold (Morse theory). I will review the basics of Morse theory and some related topics.

date:
2012/02/09 1610-1730
room:
A739
title:
Higher-order generalization of Fukaya's Morse homotopy invariant of 3-manifolds
speaker:
abstract:

We give a higher order generalization of Fukaya's Morse homotopy theoretic approach to 2-loop Chern--Simons perturbation theory. In this talk, we construct a sequence of invariants of homology 3-spheres with values in a space of trivalent graphs (Jacobi diagrams) by using Morse homotopy theory.

date:
2012/01/05 1000-1130
room:
A739
title:
An Introduction to Model Theory
speaker:
Kota Takeuchi (University of Tsukuba)
abstract:

This talk will be a brief introduction to the Model Theory. We will discuss a model theoretic viewpoint over mathematics and, especially, algebra.This talk assumes no prior knowledge of logic.

date:
2012/01/05 1230-1400
room:
A739
title:
Topology of hyperplane arrangements
speaker:
Masahiko Yoshinaga (Kyoto University)
abstract:

I will survey several results concerning topology of hyperplane arrangements with focus on the fundamental group. (Kew words: homotopy type, K(\pi, 1) space, minimality, fundamental group.)

date:
2012/01/04 1500-1700
room:
A739
title:
Definable Morse functions in a real closed field
speaker:
Tomohiro Kawakami (Wakayama University)
abstract:

Let $X$ be a definably compact definable $C^r$ manifold and $2 \le r <\infty$. Then the set of definable Morse functions $Def_{Morse}^r(X)$ is open and dense in the set $Def^r(X)$ of definable $C^r$ functions on $X$ with respect to the definable $C2$ topology.

date:
2011/11/09 1700-1800
room:
A739
title:
Toric degenerations of integrable systems on Grassmannians
speaker:
Yuichi Nohara (Kagawa University)
abstract:

An integrable system on a symplectic manifold of dimension 2n is an n-tuple of independent functions which are mutually Poisson commutative. Moment maps of torus actions on toric varieties are typical example of integrable systems. I would like to talk about integrable systems on the Grassmannians of two-planes, and their deformations into toric moment maps. We also discuss a relation to bending Hamiltonians on the moduli space of polygons in the Euclidean three-space. This is a joint work with K. Ueda.

### Original Studio Phones Seminar Archives

date:
2011/08/23 1030-1130
room:
StudioPhones Room301B
title:
On ring theoretic invariants of quasi-isometry
speaker:
Hokuto Morishima (Osaka University)
abstract:

We consider a certain ring for a finitely generated group, and introduce the results about correspondence of the ring and the quasi-isometric geometry of the finitely generated group.

date:
2011/08/23 1300-1400
room:
StudioPhones Room301B
title:
On pre-computable category
speaker:
Yusuke Kiriu (Studio Phones)
abstract:

This talk is a brief survey of pre-computable category, especially, for topological objects, invariant functions, and algebraic structures. On the background of our research, we are studying computer sciences, logics and linguistics. I also talk about some details of pre-computable category within the context of 2 and 3 dimensional computer graphics and general graphics.

date:
2011/08/23 1410-1800
room:
StudioPhones Room301B
title:
Introduction to Schubert calculus
speaker:
Shizuo Kaji (Yamaguchi University)
abstract:

"How many lines are there in the three space which meet all the four given lines ?" In 19th century, H.Schubert considered this problem in an insightful but not rigorous way. He invented a symbolic "calculation'' for the conditions on lines as follows: [intersecting a given line]^{\cap 4} =   [lying on a given line] \cup [lying on a given line], and obtained the answer two. In fact, the "algebra'' of the conditions on lines is isomorphic to the ring of the symmetric polynomials called Schur polynomials. D.Hilbert asked for a rigorous foundation for the above calculus as the 15th problem in his 1900 lecture and now Schubert’s quiz can be rephrased in terms of cohomology, or equivalently, intersection theory of a Grassmaniann manifold. In this talk, I will briefly review the basics of Schubert calculus with a focus on the correspondence of several algebras occurring in this subject including the above one.

date:
2011/03/08 1500-1800
room:
StudioPhones Room301B
title:
Vertex operator algebras and characters of their modules
speaker:
Yusuke Arike (Osaka University)
abstract:

I will explain about Zhu's modular invariance property of characters of modules for rational vertex operator algebras.

date:
2010/07/29 1300-1700
room:
StudioPhones Room301B
title:
On the tetrahedral number of hyperbolic manifolds of bounded volume
speaker:
Yo'av Rieck (University of Arkansas) after Jorgensen and Thurston, joint with Tsuyoshi Kobayashi
abstract:

In the 70's, Jorgensen and Thruston proved that for any V>0 there exists a finite collection of manifolds X_1,...,X_n so that any complete hyperbolic 3-manifold of volume at most V is obtained by filling some X_i.  A well-know "folk theorem" of Thruston says that there exists a constant K so that X_i can be triangulated using at most KV tetrahedra. We will first motivate this theorem by describing two applications. The purpose of this talk is providing a proof of Thurston's theorem. The proof follows an outline that appeared in the litrature, but as remarked by Benedetti and Petronio, it requirs control over the intersection between the Voronoi cells and the thin and thick parts of the manifolds (the terms will be explained in the talk).  We will show how we control these intersections. Most of the work is elementary and done in hyperbolic 3-space. I will make an effort to make it accessible to students familiar with the upper half space model.

date:
2010/03/15 1300-1700
room:
StudioPhones Room301B
title:
On a variation of the Gordian complex
speaker:
In Dae Jong (Osaka City University)
abstract:

This is a joint work with Kazuhiro Ichihara. We will introduce simplicial complexes by using various invariants and local moves on knots, which give generalizations of the Gordian complex defined by Hirasawa and Uchida. In this talk, we will study simplicial complexes defined by using the Alexander-Conway polynomial and the crossing change or the Delta-move. We will show that these simplicial complexes are Gromov hyperbolic.

date:
2010/02/17 1300-1500
room:
StudioPhones Room301B
title:
On roots of Dehn twists
speaker:
Naoyuki Monden (Osaka University)
abstract:

Margalit and Schleimer constructed nontrivial roots of the Dehn twist about a nonseparating curve.We prove that the conjugacy classes of roots of the Dehn twist about a nonseparating curve correspond to the conjugacy classes of periodic maps with certain conditions.Furthermore, we give data set which determine the conjugacy class of a root. As a consequence, we can find the minimum degree and the maximum degree, and show that the degree must be odd. Also, we give Dehn twist expression of the root of degree 3

date:
2010/02/17 1500-1830
room:
StudioPhones Room301B
title:
Handle decompositions of knot complements
speaker:
Tsubasa Ichikawa (Osaka University)
abstract:

Every smooth compact n-manifold is decomposed into some copies of n-disks (= handles) according to certain rules. I would like to introduce handle decompositions of manifolds (especially knot complements) and demonstrate how to draw them.

date:
2010/02/13 1000-1130
room:
StudioPhones Room301B
title:
Quandles and related topics
speaker:
Yuichi Kabaya (Osaka City University Advanced Mathematical Institute (OCAMI))
abstract:

Quandle is an algebraic structure which was introduced by David Joyce in 1982, motivated by knot theory and conjugation of a group. In this talk I will introduce several aspects of quandles and related topics; quandle homology and relation with group homology, rack space, (twisted) Alexander polynomial, etc.

date:
2010/02/13 1300-1730
room:
StudioPhones Room301B
title:
Iwasawa theory and characteristic invariants
speaker:
Kazuma Shimomoto Joint with T.Ochiai (Osaka University)
abstract:

In recent years, several people have suggested the various kinds of Iwasawa Main Conjecture formulated in the language used in their own field of study. In this talk, I begin with a brief review on classical Iwasawa theory, including the classical Main Conjecture. Then I move on to the p-adic modular forms, L-functions, and the Main Conjecture. The main theme of this talk is to discuss Bertini-type theorem and characteristic invariants which also serve as strategic tools to study similar invariants in toplogy and algebra.

date:
2010/02/10 0930-1130
room:
StudioPhones Room301B
title:
Application of Length of Quandle 3-Cocycle to Surface-Knot Theory
speaker:
Shin Satoh (Kobe University)
abstract:

The homology and cohomology theory of a quandle is useful to study knotted surfaces in 4-space. We define the length of a 3-cocycle of a quandle equipped with a quandle-set, and calculate the lengths of some 3-cocycles. We give lower bounds of the triple point number of a surface-knot by the length of a quandle 3-cocycle.

date:
2010/02/10 1300-1730
room:
StudioPhones Room301B
title:
On quandle homology groups of Alexander quandles of prime order
speaker:
Takefumi Nosaka (RIMS, Kyoto University)
abstract:

Our result is to determine all quandle homology groups of Alexander quandle of prime order. The proof is obtained from the calculations of quandle 'co'homology group with the generators (cocycles) by means of calculus over positive characteristic, which is inspired by T.Mochizuki's computations of third degree cocycles.  This talk outlines the proof, and our goal is to illustate why 'the higher degree cocycles are constructed from lower degree ones, and linear independently generate the quandle cohomology group'.

date:
2009/12/30 1000-1300
room:
StudioPhones Room301B
title:
Similarity between Alexander-Fox Theory and Iwasawa Theory
speaker:
Teruhisa Kadokami (Dalian University of technology)
abstract:

I explain about similarity between Alexander-Fox Theory from Knot Theory, and Iwasawa Theory from Number Theory.

date:
2009/12/30 1430-1630
room:
StudioPhones Room301B
title:
On F-coherent rings
speaker:
Kazuma Shimomoto
abstract:

I will talk about a new class of Noetherian rings defined by the Frobenius map and discuss its basic properties. The talk will also focus on some open questions.

date:
2009/12/30 1430-1730
room:
StudioPhones Room301B
title:
Bertini type theorem and Iwasawa Main Conjecture
speaker:
Kazuma Shimomoto Joint with T.Ochiai (Osaka University)
abstract:

Iwasawa Main Conjecture (IMC) in two variables was proposed by several people and proved by K.Rubin in the classical case.  More recently, T.Ochiai formulated IMC over some type of deformation spaces and he proved it in the case when the deformation space is the Iwasawa algebra.His idea is to take sufficiently many hypersurfaces and analyze the problem on them.I will talk about the so-called Bertini type theorem to generalize IMC to more general deformation spaces.

date:
2009/12/05 1000-1800
room:
2nd Floor, Lecture Room, Kanazawa University Satellite Plaza
title:
Godel's incompleteness theorem and its application
speaker:
Shunsuke Yatabe (National Institute of Advanced Industrial Science and Technology)
abstract:

In this talk, we introduce an overview of a proof of Godel's incompleteness theorem. First we see the details of arithmetization of natural number theory, then we see how Godel sentence is constructed. Then we see the arithmetical hierarchy and its "circular structure" in Global sense. If we have enough time, we also try to see some facts about non-standard model of Arithmetic.

date:
2009/10/08 1300-1800
room:
StudioPhones Room301B
title:
An Application of Category Theory to Systems Biology
speaker:
Taichi Haruna (Kobe University/JST)
abstract:

We propose a new data analytical tool for directed networks by using category theory. We develop a category theoretical treatment of directed networks in order to obtain functional networks for real networks. By applying our method to concrete data on real information processing biological networks, we find a distinguishing global structure of functional networks. We discuss a possibility of a new hypothesis on network motifs based on our theory and data analysis. We also present a glimpse of calculations when our method is thought of an abstract graph transformation.

date:
2009/10/14 1000-1200
room:
StudioPhones Room301B
title:
Cohen-Macaulay modules over Gorenstein rings
speaker:
Tokuji Araya (Nara University of Education)
abstract:

Gorenstein rings have nice homological properties to investigate the category of finitely generated modules. In this talk, I will give some basic properties of Cohen-Macaulay modules over Gorenstein rings.

date:
2009/10/14 1500-1700
room:
StudioPhones Room301B
title:
Cohen-Macaulay modules over Gorenstein rings
speaker:
Tokuji Araya (Nara University of Education)
abstract:

Gorenstein rings have nice homological properties to investigate the category of finitely generated modules. In this talk, I will give some basic properties of Cohen-Macaulay modules over Gorenstein rings.

date:
2009/09/27 1000-1300
room:
StudioPhones Room301B
title:
Basics of plane curves
speaker:
Hisanori Ohashi (RIMS, Kyoto University)
abstract:

I will give an introduction to algebraic geometry. We will see several aspects of algebraic curves, being as conscious to the general theory as possible. If time permits, I will explain the Mathieu group, the first generation of the Happy Family of finite simple sporadic groups.

date:
2009/09/27 1400-1600
room:
StudioPhones Room301B
title:
Geometry of second order PDE
speaker:
abstract:

This is an introduction to exterior differential systems. I will talk the classical theory given by E.Cartan.

date:
2009/09/27 1600-1800
room:
StudioPhones Room301B
title:
Symbolic Manipulation for pure functions
speaker:
Yusuke Kiriu (Studio Phones)(Joint with T.Sakasai)
abstract:

Beginning with a short introduction to symbolic and numeric computation, we discuss interaction between computer science and low-dimensional topology, especially, algorithms and programming paradigms. In this talk, we give an extension language designed specifically to symbolic manipulaton of pure functions by using low-level structures of Mathematica .

date:
2009/09/25 1830-2000
room:
StudioPhones Room301B
title:
Kirby's theorem
speaker:
abstract:

Using Cerf theory Kirby proved that two framed links represent diffeomorphic closed 3-manifolds if and only if they are related to each other by a sequence of "Kirby moves" on framed links. A rough sketch of Kirby's proof is explained along his original paper.

date:
2009/08/22 1000-1500
room:
StudioPhones Room301B
title:
Towards on analogy of Dehn surgery in number theory
speaker:
Yasushi Mizusawa (Nagoya Institute of Technology)
abstract:

Based on the analogy between Galois groups and Knot groups, we discuss on analogy of the theory of Dehn suregery for knots.

date:
2009/08/19 1300-1500
room:
StudioPhones Room301B
title:
Everywhere integral sections of elliptic surfaces
speaker:
Hisanori Ohashi (RIMS, Kyoto University)
abstract:

integral points of elliptic curves have long history in number theory and algebraic geometry. In this talk I will introduce the analogue of integral points in the elliptic surface case, originally defined by T. Shioda. To do so, I will explain elliptic surfaces, their Mordell-Weil lattices, related sphere packings, lattice theory and group theory. The purpose is to overview the subject.

date:
2009/08/17 1500-1800
room:
StudioPhones Room301B
title:
Lefschetz fibrations and Teichmuller spaces
speaker:
Hiroshige Shiga (Tokyo Institute of Technology)
abstract:

We discuss interaction  between Teichmuller spaces and hoomorphic Lefschetz fibrations.

date:
2009/08/17 1230-1730
room:
StudioPhones Room301B
title:
Invariants and constructions of Lefschetz fibrations
speaker:
Hisaaki Endo (Osaka University)
abstract:

Beginning with a short introduction to 4-manifolds, we discuss various properties of Lefschetz fibrations, especially, signature of Lefschetz fibrations and substitution technique for positive relations.

date:
2009/08/16 1000-1200
room:
StudioPhones Room301B
title:
Lens spaces and some invariants
speaker:
Motoo Tange (RIMS, Kyoto University)
abstract:

The speaker shall define 3-dimensional lens spaces in some ways and shall compute various topological invariants. We will consider whether we can investigate the Dehn surgery problem from the values.

date:
2009/08/16 1300-1730
room:
StudioPhones Room301B
title:
Lens spaces and some invariants
speaker:
Motoo Tange (RIMS, Kyoto University)
abstract:

The speaker shall define 3-dimensional lens spaces in some ways and shall compute various topological invariants. We will consider whether we can investigate the Dehn surgery problem from the values.

date:
2009/07/25 1000-1200
room:
StudioPhones Room301B
title:
Standard models of Train tracks
speaker:
Hideki Miyachi (Osaka University)
abstract:

In this talk, we will survey properties of the standard models of train tracks.

date:
2009/07/18 1300-1730
room:
StudioPhones Room301B
title:
Dualizing complex of the Stanley ring associated with a simplicial poset
speaker:
Kohji Yanagawa (Kansai University)
abstract:

In 1991, R. Stanley assigned a commutative ring $A_P$ to a finite simplicial poset $P$ for a combinatorial purpose. Recently, M. Masuda et al. studied $A_P$ as the equivariant cohomology ring of a torus manifold. In this talk, we give a concise description of the dualizing complex of $A_P$, and show an application.

date:
2009/05/30 1030-1130
room:
StudioPhones Room301B
title:
Schubert calculus and combinatorics of words
speaker:
Hiroshi Naruse (Okayama University)
abstract:

In this talk I will explain how combinatorics of words can be used in Schubert calculus, i.e. reducing the problem to calculate topological invariants for Schubert varieties in terms of subword combinatorics of Coxeter groups. There are recurrence relations for canonical classes and structure constants, and explicit formulas for the solutions are given for some special cases.

date:
2009/05/30 1300-1800
room:
StudioPhones Room301B
title:
How to overcome Russell paradox (within fuzzy logic)
speaker:
Shunsuke Yatabe (National Institute of Advanced Industrial Science and Technology)
abstract:

It is well known that Russell paradox shows that the naive set theory implies a contradiction within classical logic. However, in 1970's, it turned out that the theory is consistent within many non-classical logics. In this talk, we introduce the case of fuzzy logic. One of the most interesting aspect of such set theory is that it forgives the very strong form of circular definitions. However this makes difficult to construct its models. In this talk we briefly introduce about them.

date:
2009/02/23 1500-1800
room:
StudioPhones Room301B
title:
Geometric method on Virtual Knot Theory
speaker:
Teruhisa Kadokami (Dalian University of technology)
abstract:

A virtual link is an extended concept of a link in S^3 which can be realized as a diagram on S^2 by introducing virtual crossings. Geometrically, a virtual link can be considered as a link in the product space of an oriented closed surface and the closed interval. So we can study virtual links geometrically. I will introduce some geometric methods of Virtual Knot Theory.

date:
2009/02/20 1600-2030
room:
StudioPhones Room301B
title:
Teichmueller spaces and Banach spaces in the Teichmueller theory 1
speaker:
Hideki Miyachi (Osaka University)
abstract:

In this talk, I give a brief introduction of the Teichmueller theory. Especially, we will discuss the complex analytic structure of the Teichmueller space.

date:
2009/02/21 1000-1600
room:
StudioPhones Room301B
title:
Teichmueller spaces and Banach spaces in the Teichmueller theory 1
speaker:
Hideki Miyachi (Osaka University)
abstract:

In this talk, I give a brief introduction of the Teichmueller theory. Especially, we will discuss the complex analytic structure of the Teichmueller space.

date:
2009/02/21 1600-1830
room:
StudioPhones Room301B
title:
When is a Ford-like polygon non-generic?
speaker:
Akira Ushijima (Kanazawa University)
abstract:

The detail of the proof that Ford-like polygons for a given Fuchsian group are generic for almost all points will be discussed in this talk.

date:
2009/02/22 1000-1200
room:
StudioPhones Room301B
title:
Limit sets of Kleinian groups
speaker:
Kentaro Ito (Nagoya University)
abstract:

I will explain some basic properties of limit sets of Kleinian groups.

date:
2009/02/20 1300-1800
room:
StudioPhones Room301B
title:
Wrokshop
speaker:
Yusuke Kiriu(Studio Phones)
abstract:

date:
2009/02/19 1400-1800
room:
StudioPhones Room301B
title:
Toric degenerations of Gerfand-Cetlin systems and their applications
speaker:
Yuichi Nohara (Tohoku University)
abstract:

The Gelfand-Cetlin system is a completely integrable system       on a flag manifold of type A, whose moment polytope is known       as the Gelfand-Cetlin polytope.       We show that the Gelfand-Cetlin system can be deformed into       a moment map on a toric variety corresponding to the       Gelfand-Cetlin polytope.       We also discuss an application to disk counting problem.

date:
room:
StudioPhones Room301B
title:
Sutured Floer homology and its application
speaker:
Motoo Tange (RIMS, Kyoto University)
abstract:

Juhasz has defined sutured Floer homologies for sutured manifolds. We will talk about its definition, calculation, and applications.

date:
2009/01/16 1300-1600
room:
StudioPhones Room301B
title:
Foliations on 3-dimesional manifolds
speaker:
Hiroko Murai (Tokyo Denki University)
abstract:

For a given knot K in the 3-sphere , D. Gabai has given a method for constructing a taut finite depth foliations on the exterior of such that the minimal genus Seifert surface for K is a leaf of the foliation and the restriction of the foliation to the boundary is a foliation by circles. In this talk, we apply the method to 5_2 knot and see the behavior of leaves of the foliation.

date:
2008/12/13 1130-1300
room:
StudioPhones Room301B
title:
Quandle and hyperbolic volume
speaker:
Ayumu Inoue (Tokyo Institute of Technology)
abstract:

In this talk, we will show that the hyperbolic volume of a hyperbolic knot is a quandle cocycle invariant.   Further we will show that it completely determines invertibility and positive/negative amphicheirality of hyperbolic knots.

date:
2008/12/13 1430-1700
room:
StudioPhones Room301B
title:
Quandle and hyperbolic volume
speaker:
Ayumu Inoue (Tokyo Institute of Technology)
abstract:

In this talk, we will show that the hyperbolic volume of a hyperbolic knot is a quandle cocycle invariant.   Further we will show that it completely determines invertibility and positive/negative amphicheirality of hyperbolic knots.