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arXiv · 0911.4234

Quasi-morphisms on Free Groups

Pascal Rolli
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Abstract

Let F be the free group over a set of two or more generators. R. Brooks constructed an infinite family of quasi-morphisms on F such that an infinite subfamily gives rise to independent classes in the second bounded cohomology of F, which proves that this space is infinite dimensional. We give a simpler proof of this fact using a different type of quasi-morphisms. After computing the Gromov norm of the corresponding bounded classes, we generalize our example to obtain quasi-morphisms on free products, as well as quasi-morphisms into groups without small subgroups, also known as epsilon-representations.

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Pascal Rolli. 2009-11-24. Quasi-morphisms on Free Groups. https://arxiv.org/abs/0911.4234

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