Regularity for the normalized p-Laplacian equation with an arbitrary degeneracy law
Claudemir Alcantara, Makson Santos
TL;DR
The paper addresses interior regularity of viscosity solutions to the gradient-degenerate normalized $p$-Laplacian $-\sigma(|Du|)\Delta_p^{ ext{N}}u=f$, where the degeneracy is governed by a modulus $\sigma$ whose inverse satisfies a Dini condition. It extends the regularity theory by developing a non-collapsing modulus construction and a hyperplane-approximation scheme, coupled with compactness and stability analyses for scaled, shifted-derivative equations. The main achievement is proving $u\, ext{is differentiable}, i.e.,}^1_{ ext{loc}}(B_1)$ with a gradient modulus $\gamma$, under very general degeneracy laws, and without requiring Hölder continuity of the gradient in general. This work broadens the applicability of regularity results for degenerate fully nonlinear elliptic equations and provides a robust framework for handling arbitrary degeneracy via non-collapsing sets and affine-approximation iterations.
Abstract
We examine the interior regularity of solutions to a degenerate normalized $p$-Laplace equation, where the degeneracy is governed by a modulus of continuity whose inverse satisfies a Dini continuity condition. We prove that under very general assumptions on the degeneracy law, solutions belong to the $C^1$ class. We argue by approximating the solutions by a sequence of hyperplanes, which allows us to prove the desired regularity.
