Relative rigidity, quasiconvexity and C–complexes

Mj, Mahan¹

¹School of Mathematical Sciences, RKM Vivekananda University, PO Belur Math, Dt Howrah, WB-711202, India

Algebraic and Geometric Topology, Tome 8 (2008) no. 3, pp. 1691-1716

Résumé

We introduce and study the notion of relative rigidity for pairs (X,J ) where

(1)  X is a hyperbolic metric space and J a collection of quasiconvex sets,

(2)  X is a relatively hyperbolic group and J the collection of parabolics,

(3)  X is a higher rank symmetric space and J an equivariant collection of maximal flats.

Relative rigidity can roughly be described as upgrading a uniformly proper map between two such J to a quasi-isometry between the corresponding X. A related notion is that of a C–complex which is the adaptation of a Tits complex to this context. We prove the relative rigidity of the collection of pairs (X,J ) as above. This generalises a result of Schwarz for symmetric patterns of geodesics in hyperbolic space. We show that a uniformly proper map induces an isomorphism of the corresponding C–complexes. We also give a couple of characterizations of quasiconvexity of subgroups of hyperbolic groups on the way.

Détail

DOI : 10.2140/agt.2008.8.1691

Keywords: Hyperbolic group, Quasiconvex subgroup, flats, relative hyperbolicity

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