On sets with unit Hausdorff density in homogeneous groups

Abstract

It is a longstanding conjecture that given a subset $E$ of a metric space, if $E$ has finite Hausdorff measure in dimension $\hat{I}\pm \ge 0$ and ${\mathcal{H}}^{\hat{I}}\pm └E$ has unit density almost everywhere, then $E$ is an $\hat{I}\pm$-rectifiable set. We prove this conjecture under the assumption that the ambient metric space is a homogeneous group with a smooth-box norm.

19 pages