Infinite groups with fixed point properties

Abstract

We construct finitely generated groups with strong fixed point properties. Let ${\mathcal{X}}_{ac}$ be the class of Hausdorff spaces of finite covering dimension which are mod-$p$ acyclic for at least one prime $p$. We produce the first examples of infinite finitely generated groups $Q$ with the property that for any action of $Q$ on any $X\in {\mathcal{X}}_{ac}$, there is a global fixed point. Moreover, $Q$ may be chosen to be simple and to have Kazhdan's property (T). We construct a finitely presented infinite group $P$ that admits no non-trivial action by diffeomorphisms on any smooth manifold in ${\mathcal{X}}_{ac}$. In building $Q$, we exhibit new families of hyperbolic groups: for each $n\ge 1$ and each prime $p$, we construct a non-elementary hyperbolic group $G_{n,p}$ which has a generating set of size $n+2$, any proper subset of which generates a finite $p$-group.

Version 2: 29 pages. This is the final published version of the article

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