The MathNet Korea
Information Center for Mathematical Science

### 세미나

Information Center for Mathematical Science

#### 세미나

##### 서울대학교 수학강연회
• Title : Bargaing among Groups
• Speaker : 체수찬
• Data : 2008-09-18 16:00:00
• Host : 서울대학교 수학과
• Place :

##### 연세대학교 수학과 콜로퀴움
• Title : Singularities of Log Pairs
• Speaker : 박지훈
• Data : 2008-12-04 170:00:00
• Host : 연세대학교 BK21 수리과학사업단
• Place :

##### KAIST Discrete Math Seminar

A map is a 2-cell embedding of a graph into a closed surface and a regular map is a highly symmetric map like five Platonic solids. A map is not merely a topological object. It is also a sequence of permutations, which provides a relation to group theory, and a ramified covering of the Riemann sphere, which gives a relation to Riemann surface. Furthermore, it can be realized by a complex algebraic curve called Belyi function. In this talk, classifications of regular maps are considered from several aspect. And, some connections between maps and permutation group, Riemann surface and Belyi functions and their applications are given.

##### KAIST Discrete Math Seminar

The Gram matrix is a basic tool for studying quadratic forms. However, no Gram matrix can be constructed for quadratic forms defined over number fields. This makes the study about representation of quadratic forms so difficult. We will define a formal Gram matrix and look over several applications

##### KAIST Discrete Math Seminar

Many problems in discrete and computational geometry can be reduced to combinatorial questions concerning systems of segments or triangles in the plane. In spite of what (little) we can say about these planar questions, much less is known in higher dimensions. In this talk we will survey some of these questions and classical results, and present the following theorem: Let d>2 and n>d+1 and P a set of n points in d-dimensional Euclidean space. Then P contains a subset Q of d points such that for any point p in P, the simplex spanned by Q and p does not contain the origin in its interior. This answers a question by R.Strausz, and along the way we strengthen the Colored Helly and Caratheodory theorems, due to L. Lovász and I. Bárány, respectively. ----------------------------------------------Informations on future talks can be found at :http://mathsci.kaist.ac.kr/~sangil/seminar/Please email to sangil (at) kaist.edu if you wish to receive thisannouncements in the future by email.