Coarse quotients of metric spaces and embeddings of uniform Roe algebras

Abstract

We study embeddings of uniform Roe algebras which have “large range” in their codomain and the relation of those with coarse quotients between metric spaces. Among other results, we show that if $Y$ has property A and there is an embedding $\Phi:\mathrm{C}^\_u(X)\to\mathrm{C}^u(Y)$ with “large range” and so that $\Phi(\ell\infty(X))$ is a Cartan subalgebra of $\mathrm{C}^\*\_u(Y)$, then there is a bijective coarse quotient $X\to Y$. This shows that the large-scale geometry of $Y$ is, in some sense, controlled by the one of $X$. For instance, if $X$ has finite asymptotic dimension, so does $Y$.