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**第9回 [#d33af6ab]
日時 	2009年3月18日(水) 15:30-16:30

会場 	西8号館W棟8階W1008号室

講演者 	高橋渉教授(東京工業大学)

題目 	Proximal Point Algorithms and Four Nonlinear Resolvents in Optimization

**第8回 [#ad2ed071]
日時 	2009年3月5日(木) 15:00-16:30

会場 	西8号館W棟8階W1008号室

講演者 	吉田真紀氏(大阪大学)

題目 	情報セキュリティ研究生活と大阪大学における男女共同参画の取り組み



**第7回 [#q73de41a]
日時 	2009年2月19日(木) 14:00-15:00

会場 	西8号館W棟8階W809号室

講演者 	Sunyoung Kim 教授(Ewha W. University)

題目 	A Sparse Version of Full Semidefinite Programming Relaxation for Sensor Network Localization Problems


Semidefinite programming relaxation has become an important tool for sensor network localization after Biswas and Ye's work. We discuss a MATLAB software package called "a sparse version of full semidefinite programming relaxation (SFSDP)." SFSDP is proposed to improve the efficiency of the full semidefinite programming relaxation by Biswas and Ye by exploiting the sparsity of the problem. Thus, the size of the resulting SDP relaxation is reduced and much larger-sized problems can be handled. Numerical results show better computational performance of SFSDP than any other available methods.

At the end of the talk, the status of women in science and engineering in Korea will be discussed briefly, as a part of promoting women in science program.

**第6回 [#vcfb88d2]

日時 	2008年12月12日(金) 15:00-16:00

会場 	西8号館W棟10階W1008号室

講演者 	Professor Anthony To-Ming Lau (University of Alberta)

題目 	Separation and extension properties for positive definite functions for groups


A well known theorem of Hahn Banach asserts that if E is a closed subspace of a Banach space and F is a closed subspace of E, then each continuous linear functional on F can be extended to a continuous linear functional on E. As a consequence, any element in E but not in F can be separated by continuous linear functional on E. In my talk, I shall discuss similar properties for closed subgroups of a locally compact group and their relations with the invariant complementation problem for the group von Neumann algebra of a locally compact group.

**第5回 [#z6eeb808]

日時 	2008年10月22日(水) 15:30-17:30

会場 	西8号館W棟10階W1008号室
講演者 	古宇田悠哉(Yuya KODA)

題目 	Colored Turaev-Viro invariants of twist knots


至るところが3次元ユークリッド空間と同相な近傍を持つ空間を3次元多様体という.向き付けられた3次元多様体$M$と,その中に埋め込まれた有向絡み目$L$,すなわち向きが指定されたいくつかの円周のイソトピー類,の対$(M,L)$に対し,色付きTuraev-Viro不変量とよばれる不変量が Barrett,Garcia-Islas,Martinsの3氏により導入された.この不変量は,イニシャルデータとよばれるある代数的な情報と,これに付随して与えられる絡み目の"色"が与えられるごとに定義されるものであり, 3次元多様体$M$とその中の絡み目$L$の対$(M,L)$に対して"真の意味"で定義される不変量である.本講演では,ツイスト結び目とよばれる3次元球面内の結び目のクラスに対するこの不変量の計算方法と計算結果を紹介する.時間が許せば,レンズ空間内の同種のクラスに対する計算結果も紹介する.

2 講演者 	安永憲司(Kenji YASUNAGA)

題目 	誤り訂正符号における誤りの単調性を利用した訂正能力分析」
"Analysis of error correcting codes using the monotone error structure"


最小距離がdである誤り訂正符号を使えば、d/2個未満の誤りは必ず訂正することができる。 d/2個以上の誤りが発生した場合でも誤り個数がd/2付近であれば、多くの誤りが訂正可能であることが知られている。しかし、この問題に対する理論的分析はそれほど進んでいるとはいえない。講演者はこれまでに、d/2個以上の誤りが発生した場合の訂正可能誤り数について、誤りの単調性を利用した分析を行ってきた。本講演ではその成果について説明する。

**第4回 [#uc8a9498]
日時 	2008年10月1日(水) 13:30-14:30

会場 	西8号館W棟10階W1008号室

講演者 	Professor Suhyoung Choi (KAIST)

題目 	A survey of projective geometric structures on 2-, 3-manifolds


We go over definitions of classical geometries including projective geometry. We discuss manifolds with geometric structures on them and their significance. Finally, we discuss manifolds with projective structures and many recent advances and some questions that we are working on using algebraic and numerical computations.

**第3回 [#mfda0af3]
日時 	2008年9月1日(月) 13:30-14:30

会場 	西8号館W棟8階W809号室

講演者 	Dr. Aapo Hyvärinen (Professor of Computational Data Analysis, University of Helsinki, Finland)

題目 	From independent component analysis to score matching


I will start the talk by reviewing the basic concepts of independent component analysis (ICA), and its application to learning Bayesian networks. Generalizations of ICA serve as one motivation for the main topic of the talk: estimation of probabilistic models which are not normalized, i.e. they do not integrate into unity.

Normalization is, in principle, always possible by numerical integration, but it is often computationally very difficult. To solve this problem, I introduced a new estimation principle: score matching (JMLR, 2005). The point is to look at some derivatives of the log-densities which do not depend on the normalization of the model at all. The objective function is given in closed form and can be readily minimized by conventional optimization techniques, thus avoiding any numerical integration. The ensuing estimation method can also be shown to have some statistical optimality properties in Bayesian denoising, and leads to a new kind of information geometry.


**第2回 [#y7baa212]

日時 	2008年7月9日(水) 13:30-14:30

会場 	西8号館W棟10階W1008号室

講演者 	Paul Dow 氏

題目 	Recent Progress in Finding Exact Treewidth


The treewidth of a graph is a scalar value that measures how easily a graph can be decomposed into a tree. Many NP-hard problems can be solved in polynomial time when restricted to graphs with bounded treewidth. Additionally, treewidth is central to several active areas of artificial intelligence research, including probabilistic reasoning and constraint satisfaction. In these research areas, the ability to find the exact treewidth of a graph can have a significant impact on the size and difficulty of problems that can be solved. Unfortunately, finding the treewidth of a general graph is NP-hard, and it is not known whether a polynomial-time, constant-factor approximation is possible. In this talk, I will discuss new techniques that have allowed us to find the treewidth of ever larger and more difficult graphs. The techniques I will discuss come from the area of heuristic search algorithms, including best-first search, breadth-first heuristic search, iterative deepening, and the use of external memory via delayed duplicate detection.

**第1回 [#e819b216]

日時 	2008年5月12日(月) 13:30-14:30

会場 	西8号館W棟10階W1008号室

講演者 	Manindra Agrawal 氏 (Indian Institute of Technology Kanpur)

題目 	Basic Tools of Computational Algebra


Algorithms for a number of problems of both theoretical and practical importance have been designed with the help of algebra. For example, coding messages, cryptography, image compression, integer factorization, primality testing, polynomial factorization etc. Nearly all of these algorithms use only basic tools of algebra. In this talk, I will give an overview of some of these and discuss their usage.