Invariance of non-vanishing of first $l^p$-cohomology under $L^q$-Measured Equivalence

Abstract

The first $l^p$-cohomology is an algebro-analytical object attached to a finitely generated discrete group and introduced by M. Gromov. It is well known that it is invariant under quasi-isometry. In this article, we prove that the non-vanishing of the first $l^p$-cohomology of a non-amenable group is invariant under $L^q$-Measured Equiavalence (an equivalence relation introduced by Gromov), where $q\geq p$. We also discuss many applications of this result. We prove that for hyperbolic (in the sense of Gromov) Coxeter groups with boundaries having Combinatorial Loewner Property, conformal dimension (of the canonical conformal gauge) of the Gromov boundary is invariant under $L^q$-Measured Equivalence for some large $q$. We prove that the finitely generated free groups and surface groups are not $L^1$-Measured Equivalent. We also give a lower bound of the critical exponent for the first $l^p$-cohomology of any lattice in $SO(n,1)$. Finally, we discuss $L^q$-Measured Equivalence between non-amenable 3-manifold groups corresponding to Thurston's three geometries $\mathbb{H}^3$, $\mathbb{H}^2\times\mathbb{R}$ and $\widetilde{SL_2(\mathbb{R})}$.