# Porosity and differentiability of Lipschitz maps from stratified groups to Banach homogeneous groups

created by pinamonti on 06 Jun 2017

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Submitted Paper

Inserted: 6 jun 2017
Last Updated: 6 jun 2017

Year: 2017

Abstract:

Let $f$ be a Lipschitz map from a subset $A$ of a stratified group to a Banach homogeneous group. We show that directional derivatives of $f$ act as homogeneous homomorphisms at density points of $A$ outside a $\sigma$-porous set. At density points of $A$ we establish a pointwise characterization of differentiability in terms of directional derivatives. We use these new results to obtain an alternate proof of almost everywhere differentiability of Lipschitz maps from subsets of stratified groups to Banach homogeneous groups satisfying a suitably weakened Radon-Nikodym property. As a consequence we also get an alternative proof of Pansu's Theorem.