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Bounded cohomology and isometry groups of hyperbolic spaces

Ursula Hamenstaedt
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Abstract

Let X be an arbitrary hyperbolic geodesic metric space and let G be a countable non-elementary weakly acylindrical group of isometries of X. We show that the second bounded cohomology group of G with real coefficients or with coefficients in the regular representation is infinite dimensional. The result holds for any subgroup of the mapping class group of a non-exceptional surface of finite type not containing a normal subgroup which virtually split as a direct product.

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Ursula Hamenstaedt. 2006-09-30. Bounded cohomology and isometry groups of hyperbolic spaces. https://arxiv.org/abs/math/0507097

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