Local bounds, Harnack inequality and Hölder continuity for divergence type elliptic equations with nonstardard growth

Abstract

In this paper we obtain a Harnack type inequality for solutions to elliptic equations in divergence form with non-standard $p(x)-$type growth. A model equation is the inhomogeneous $p(x)-$laplacian. Namely, \[ Δ_{p(x)}u:=\mbox{div}\big(|\nabla u|^{p(x)-2}\nabla u\big)=f(x)\quad\mbox{in}\quadΩ\] for which we prove Harnack inequality when $f\in L^{q_0}(\Omega )$ if $\max \{1,\frac{N}{p_{min}}\}<q_0\le \infty$. The constant in Harnack inequality depends on $u$ only through $\Vert |u{|}^{p(x)}{\Vert }_{L^1(\Omega )}^{p_{max}-p_{min}}$. Dependence of the constant on $u$ is known to be necessary in the case of variable $p(x)$. As in previous papers, log-Hölder continuity on the exponent $p(x)$ is assumed. We also prove that weak solutions are locally bounded and Hölder continuous when $f\in L^{q_0(x)}(\Omega )$ with $q_0\in C(\Omega )$ and $\max \{1,\frac{N}{p(x)}\}<q_0(x)$ in $\Omega$. These results are then generalized to elliptic equations \[ \mbox{div}A(x,u,\nabla u)=B(x,u,\nabla u) \] with $p(x)-$type growth.

Cited by in corpus (2)

• A Carleson type inequality for fully nonlinear elliptic equations with non-Lipschitz drift term
• The boundary Harnack inequality for variable exponent $p$-Laplacian, Carleson estimates, barrier functions and $p(\cdot )$-harmonic measures