The second bounded cohomology of a group acting on a Gromov-hyperbolic space
نویسنده
چکیده
Suppose a group G acts on a Gromov-hyperbolic space X properly discontinuously. If the limit set L(G) of the action has at least three points, then the second bounded cohomology group of G, H 2 b (G;R) is in nite dimensional. For example, ifM is a complete, pinched negatively curved Riemannian manifold with nite volume, thenH 2 b ( 1 (M);R) is in nite dimensional. As an application, we show that if G is a knot group with G 6' Z, then H 2 b (G;R) is in nite dimensional.
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