Sharp gradient estimates for quasilinear elliptic equations with $p(x)$ growth on nonsmooth domains

TL;DR

This paper establishes sharp gradient estimates for quasilinear elliptic equations with variable exponent growth on nonsmooth domains, bridging a gap in previous estimates and extending results to broader domain classes.

Contribution

It provides the endpoint Calderón-Zygmund estimates for $p(x)$-Laplacian equations on nonsmooth domains, improving a priori estimates below $p(x)$ and broadening the class of admissible domains.

Findings

Achieved sharp gradient estimates at the endpoint case.

Extended estimates to larger classes of nonsmooth domains.

Improved a priori estimates below $p(x)$.

Abstract

In this paper, we study quasilinear elliptic equations with the nonlinearity modelled after the $p(x)$-Laplacian on nonsmooth domains and obtain sharp Calder\'on-Zygmund type estimates in the variable exponent setting. In a recent work of \cite{BO}, the estimates obtained were strictly above the natural exponent and hence there was a gap between the natural energy estimates and estimates above $p(x)$, see \eqref{energy_introduction} and \eqref{byun_ok_estimate}. Here, we bridge this gap to obtain the end point case of the estimates obtained in \cite{BO}, see \eqref{our_estimate}. In order to do this, we have to obtain significantly improved a priori estimates below $p(x)$, which is the main contribution of this paper. We also improve upon the previous results by obtaining the estimates for a larger class of domains than what was considered in the literature.