Hausdorff measure of the singular set of quasiregular maps on Carnot groups
It is proved that the \((i-m-1)\)-dimensional Hausdorff measure of the image of the branch set of a quasiregular mapping on the Carnot group is positive (\(i\) is the homogeneous dimension of the Carnot group and \(m\) is the index of the last vector space of the corresponding Lie algebra).
scientific article; zbMATH DE number 2012531