Inserted: 15 sep 2015
Last Updated: 8 nov 2018
Journal: Ann. Acad. Sci. Fenn. Math.
We observe that upper densities and spherical Federer densities may differ on all two dimensional surfaces of the sub-Riemannian Heisenberg group. This provides an entire class of intrinsic rectifiable sets having upper density strictly less than one.
Keywords: Hausdorff measure, Heisenberg group, spherical measure, density, rectifiability