過去のセミナー/2009年度の履歴(No.4)

2009年度組合せ数学セミナー†

3月16日
14:00-14:50	徳重典英（琉球大教育）	$n$次元立方体の中の大きな$n$次元正則単体
15:05-15:35	篠原雅史（鈴鹿高専）	低い次元における距離集合について
15:45-16:15	谷口哲至（松江高専）	On graphs with the smallest eigenvalue at least $-\frac{1}{2}(3+\sqrt{5})$ --an irreducibility of Hoffman graphs--
16:25-16:55	篠原英裕（大阪大情報）	有限群の near-factor と関連するグラフについて

3月17日
9:30-10:15	須田庄（東北大情報）	Mutually unbiased bases に関連する組合せ構造（その１）
10:30-11:00	田中利恵（東北大情報）	Classification of commutative association schemes with almost commutative Terwilliger algebras
11:10-11:40	北詰正顕（千葉大理）	Neighbors of the Leech lattice
13:30-14:20	坂内英一（九大数理）	$t$-designs in real hyperbolic spaces
14:30-15:00	三枝崎剛（北大理）	Conformal designs of lattice type vertex operator algebras
15:20-15:50	田辺顕一朗（北大理）	有限群の作用で不変な部分微分体上の頂点代数としての有限次元加群
16:00-16:15	重住淳一（九大数理)	A new example of Euclidean tight 6-design
16:20-16:35	佐野良夫（京大数理)	The competition-common enemy graphs of digraphs satisfying the conditions $C(p)$ and $C'(p)$
16:40-16:55	谷口浩朗（香川高専)	On $d$-dimensional Buratti-Del Fra type dual hyperovals in $PG(3d, 2)$
17:30-19:30	懇親会(JoliPort)

3月18日
9:30-10:15	須田庄（東北大情報）	Mutually unbiased bases に関連する組合せ構造（その２）
10:30-11:00	知念宏司（近畿大理工）	非自己双対 Golay 符号から作られる不変式のRiemann 予想について
11:10-11:40	田村宏樹（東北大情報）	Extended constacyclic codes
11:50-12:20	吉田知行（北大理)	対称群を使った分割表のランダムサンプリングと一致数の正確な生起確率

題名: Cellular automata and groups: dynamical aspects of infinite groups
時間: 15:00～16:30
場所: 伊都キャンパス数理棟 1階 122番教室
講師: Tullio Ceccherini-Silberstein (University of Sannio)
概要:
In this talk I would like to introduce the audience to the theory of cellular automata and groups focusing on some dynamical aspects of infinite groups (amenability, residual finiteness, local finiteness, periodicity, surjunctivity and soficity). As an application, we shall also describe a solution to the Kaplansky conjecture on the stable finiteness of groups rings (with coefficients in any field) for the class of sofic groups.

題名: On the Okounkov-Vershik approach to the representation theory of the symmetric groups
時間: 15:00～16:30
場所: 伊都キャンパス数理棟 1階 122番教室
講師: Tullio Ceccherini-Silberstein (University of Sannio)
概要:
In this talk, I would like to describe the representation theory of the symmetric groups along the new lines developed by several authors, in particular by A.M. Vershik, G.I. Olshanskii and A. Okounkov. The tools/ingredients of this new approach are either completely new, or were not fully understood in their whole importance by previous authors. I'll try to analyze such tools/ingredients which consist of:
(i) the algebras of conjugacy-invariant functions, the algebras of bi-$K$-invariant functions, the Gelfand pairs and their spherical functions;
(ii) the Gelfand-Tsetlin algebras and their corresponding bases;
(iii) the branching diagrams, the associated posets and the content of a tableau;
(iv) the Young-Jucys-Murphy elements and their spectral analysis;
(v) the characters of the symmetric group viewed as spherical functions.