The author introduces a notion of hyperbolic groupoids, generalizing the notion of a Gromov hyperbolic group. Examples of hyperbolic groupoids include actions of Gromov hyperbolic groups on their boundaries, pseudogroups generated by expanding self-coverings, natural pseudogroups acting on leaves of stable (or unstable) foliation of an Anosov diffeomorphism, etc. The author describes a duality theory for hyperbolic groupoids. He shows that for every hyperbolic groupoid G there is a naturally defined dual groupoid G⊤ acting on the Gromov boundary of a Cayley graph of G. The groupoid G⊤ is also hyperbolic and such that (G⊤)⊤ is equivalent to G. Several classes of examples of hyperbolic groupoids and their applications are discussed.
[ 113 ] G . J . Murphy , C * - algebras and operator theory . Academic Press , Boston 1990 . ... [ 120 ] A . L . T . Paterson , Groupoids , inverse semigroups ... [ 121 ] G . K . Pedersen , C * - algebras and their automorphism groups .
However, we also show that this is rather exceptional: uniform lattices in semisimple Lie groups which contain p-torsion (for p ≠ 2) do not act freely on Q -acyclic Q...
Global Grothendieck Duality. Torsion sheaves. Duality for torsion sheaves. Flat base change. Consequences of the flat base change isomorphism. References 1. Preliminaries and main theorems. 10 30 42 47 58 70 85 89 First we need some ...