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Geometric Property (T)
作者姓名:Rufus WILLETT  Guoliang YU
作者单位:Department of Mathematics, University of Hawai’i at Mˉanoa.;Department of Mathematics, Texas A&M University, Shanghai Center for Mathematical Sciences.
基金项目:This work was supported by the U.S. National Science Foundation (Nos. DMS1229939, DMS1342083, DMS1362772).
摘    要:This paper discusses“geometric property (T)”. This is a property of metric spaces introduced in earlier works of the authors for its applications to K-theory. Geometric property (T) is a strong form of “expansion property”, in particular, for a sequence (Xn) of bounded degree finite graphs, it is strictly stronger than (Xn) being an expander in the sense that the Cheeger constants h(Xn) are bounded below. In this paper, the authors show that geometric property (T) is a coarse invariant, i.e., it depends only on the large-scale geometry of a metric space X. The authors also discuss how geometric property (T) interacts with amenability, property (T) for groups, and coarse geometric notions of a-T-menability. In particular, it is shown that property (T) for a residually finite group is characterised by geometric property (T) for its finite quotients.

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收稿时间:2026/11/13 0:00:00

Geometric Property (T)
Rufus WILLETT,Guoliang YU.Geometric Property (T)[J].Chinese Annals of Mathematics,Series B,2014,35(5):761-800.
Authors:Rufus WILLETT and Guoliang YU
Institution:1. Department of Mathematics, University of Hawai’i at Mānoa, Honolulu, USA
2. Department of Mathematics, Texas A&M University, College Station, USA
3. Shanghai Center for Mathematical Sciences, Shanghai, China
Abstract:This paper discusses “geometric property (T)”. This is a property of metric spaces introduced in earlier works of the authors for its applications to K-theory. Geometric property (T) is a strong form of “expansion property”, in particular, for a sequence (X n ) of bounded degree finite graphs, it is strictly stronger than (X n ) being an expander in the sense that the Cheeger constants h(X n ) are bounded below. In this paper, the authors show that geometric property (T) is a coarse invariant, i.e., it depends only on the large-scale geometry of a metric space X. The authors also discuss how geometric property (T) interacts with amenability, property (T) for groups, and coarse geometric notions of a-T-menability. In particular, it is shown that property (T) for a residually finite group is characterised by geometric property (T) for its finite quotients.
Keywords:Coarse geometry  Expander  Roe algebra  Property (T)
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