Embeddings of locally compact hyperbolic groups into Lp-spaces

Abstract

In the last years, there has been a large amount of research on embeddability properties of finitely generated hyperbolic groups. In this paper, we elaborate on the more general class of locally compact hyperbolic groups. We compute the equivariant $L_p$-compression in a number of locally compact examples, such as the groups $SO(n,1)$: by proving that the equivariant $L_p$-compression of a locally compact compactly generated group is minimal for $p=2$, we calculate all equivariant $L_p$-compressions of $SO(n,1)$. Next, we show that although there are locally compact, non-discrete hyperbolic groups $G$ with Kazhdan's property ($T$), it is true that any locally compact hyperbolic group admits a proper affine isometric action on an $L_p$-space for $p$ larger than the Ahlfors regular conformal dimension of $\partial G$. This answers a question asked by Yves de Cornulier. Finally, we elaborate on the locally compact version of property $(A)$ and show that, as in the discrete case, a locally compact second countable group has property (A) if its non-equivariant compression is greater than 1/2.