Fine boundary regularity for fully nonlinear mixed local-nonlocal problems

Abstract

We consider Dirichlet problems for fully nonlinear mixed local-nonlocal non-translation invariant operators. For a bounded $C^2$ domain $\Omega \subset \mathbb{R}^d,$ let $u\in C(\mathbb{R}^d)$ be a viscosity solution of such Dirichlet problem. We obtain global Lipschitz regularity and fine boundary regularity for $u$ by constructing appropriate sub and supersolutions coupled with a Harnack type inequality. We apply these results to obtain H\"{o}lder regularity of $Du$ up to the boundary.