Sendai Max Dehn seminar

世話人： 藤原耕二 fujiwara(at)math.tohoku.ac.jp

セミナー情報は東北大学 数学教室の セミナー案内 に載せま す。

セミナー予定：

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2006 年度

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2007.3.8(thu)2pm-3pm. C-316.
Marc Bourdon(Univ Lille)
An algebraic characterisation of quasi-Moebius homeomorphisms

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2006.10.20(Fri) 3-4pm. at Sugaku-203
Satoshi Ishiwata (Tsukuba U)
Connectivity of discrete nilpotent groups

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2006.11.29(wed). 1:30-2:30. C-316.
山形紗恵子（東北大）
論文紹介 " Homotopy of ends and boundaries of CAT(0) groups" G. Conner, M. Mihalik and S. Tschantz

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2005 年度

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2005.6.16(Th) at C-316.
Dr.Kenneth J.Shackleton (U of Southampton).
2:00-3:30. "Tight geodesics and computing distances in the curve complex."
3:30-4:30. "Curve complex embeddings and injections of mapping class groups."

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2005.5.12. 2-3pm, 3:30-4:30pm. at C-316.
Brian Bowditch (U of Southampton, TIT)
"Geometry of curve compexes and hyperbolic 3-manifolds".

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2004年度

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2004.8.17(Tue). at 518.
Mark Sapir (Vanderbilt Univ)
"Asymptotic cones of relatively hyperbolic groups and quasi-isometry rigidity".

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2004.7.21 (Wed). (1) 3-4pm, (2) 4:30-5:30pm. 数学棟 518. Danny Calegari (Cal Tech).

• 3-4pm. "Dynamical forcing of circular groups".
  abstract: Given a pair (G,a) where G is a group, and a is an element of G, define X(G,a) to be the subset of S1 consisting of all rotation numbers of a under homomorphisms from G to Homeo^+(S1). We show that the set of subsets of this form are exactly the subsets which contain 0, are invariant under x -> -x, and are closed. We also show that all such subsets can be approximated in a certain sense by restricting to (explicit) finitely presented groups G.
• 4:30-5:30pm. "Universal circles for quasigeodesic flows".
  abstract: Suppose M is a closed hyperbolic 3-manifold with a quasigeodesic flow. Then pi_1(M) acts faithfully on a circle by homeomorphisms, and preserves a pair of laminations of this circle. As a corollary, the unit ball of the Thurston norm can be detected by quasigeodesic flows (generalizing a theorem of Mosher) and there are infinitely many hyperbolic 3-manifolds without quasigeodesic flows, answering a question of Thurston.

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2004.6.11. （金）.2-3pm. 数学棟518
小沢登高氏（東大・数理）
「群の従順な境界作用とその応用」
abstract: 従順性(amenability)は群の函数解析的な 取り扱いにおいて非常に重要な概念である。 (離散)群 G が従順でないときでも、 G の適当な境界 X への作用まで込めて考えると、 (G,X) の組が従順群のように振舞うことがある。 これについて話をする。

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2004.5.27.(木). 3-4pm. C棟-316.
保坂哲也氏（宇都宮大）
"Splitting theorems for CAT(0) spaces"

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2004.5.20(木). 3-4pm. C棟-316.
塩谷隆氏（東北大）
「体積の小さい3次元多様体について」

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2003年度

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"COE" means the talk is supported partially by the COE program "Exploring New Science by Bridging Particle-Matter Hierarchy".

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2004.1.22(Thu) COE
2:00-3:30 数学棟418(changed to 518)
Yann Ollivier (Univ Paris Sud)
"Measure concentration"

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2003年12月5日（金曜） COE
14：00-15：30, 数学棟518
Peter Brinkmann(Univ of Illinois)
"Dynamics of free group automorphisms"
Abstract : We present a coarse convexity result for the dynamics of automorphisms of finitely generated free groups. As an application, we obtain an algorithm that detects whether two elements of the free group are contained in the same orbit of a given automorphism.