Global Gradient Estimates for Dirichlet Problems of Elliptic Operators with a BMO Anti-Symmetric Part

TL;DR

This paper establishes new global gradient estimates for solutions to second order elliptic equations with BMO anti-symmetric parts in various domains, improving previous results by weakening coefficient assumptions.

Contribution

It proves that a weak reverse H"older inequality implies comprehensive global gradient estimates for elliptic equations with BMO coefficients in diverse domains.

Findings

Global $W^{1,p}$ estimates under reverse H"older conditions

Gradient estimates in weighted Lebesgue, Lorentz, Morrey, Orlicz, and variable Lebesgue spaces

Improved results with weaker coefficient assumptions

Abstract

Let $n\ge2$ and $\Omega\subset\mathbb{R}^n$ be a bounded NTA domain. In this article, the authors investigate (weighted) global gradient estimates for Dirichlet boundary value problems of second order elliptic equations of divergence form with an elliptic symmetric part and a BMO anti-symmetric part in $\Omega$. More precisely, for any given $p\in(2,\infty)$, the authors prove that a weak reverse H\"older inequality with exponent $p$ implies the global $W^{1,p}$ estimate and the global weighted $W^{1,q}$ estimate, with $q\in[2,p]$ and some Muckenhoupt weights, of solutions to Dirichlet boundary value problems. As applications, the authors establish some global gradient estimates for solutions to Dirichlet boundary value problems of second order elliptic equations of divergence form with small $\mathrm{BMO}$ symmetric part and small $\mathrm{BMO}$ anti-symmetric part, respectively, on bounded Lipschitz domains, quasi-convex domains, Reifenberg flat domains, $C^1$ domains, or (semi-)convex domains, in weighted Lebesgue spaces. Furthermore, as further applications, the authors obtain the global gradient estimate, respectively, in (weighted) Lorentz spaces, (Lorentz--)Morrey spaces, (Musielak--)Orlicz spaces, and variable Lebesgue spaces. Even on global gradient estimates in Lebesgue spaces, the results obtained in this article improve the known results via weakening the assumption on the coefficient matrix.