On the properties of infinty-harmonic functions and an application to capacitary convex rings

Abstract

We study positive $infty$-harmonic functions in bounded domains. We use the theory of viscosity solutions in this work. We prove a boundary Harnack inequality and a comparison result for such functions near a flat portion of the boundary where they vanish. We also study $infty$-capacitary functions on convex rings. We show that the gradient satisfies a global maximum principle, it is nonvanishing outside a set of measure zero and the level sets are star-shaped.

Keywords

• Viscosity solutions
• boundary Harnack inequality
• infinity-Laplacian
• capacitary functions
• convex rings