Homogenization for Locally Periodic Elliptic Problems on a Domain

Abstract

Let $\Omega$ be a Lipschitz domain in $\mathbb R^d$, and let $\mathcal A^\varepsilon=-\operatorname{div}A(x,x/\varepsilon)\nabla$ be a strongly elliptic operator on $\Omega$. We suppose that $\varepsilon$ is small and the function~$A$ is Lipschitz in the first variable and periodic in the second, so the coefficients of $\mathcal A^\varepsilon$ are locally periodic. Given $\mu$ in the resolvent set, we are interested in finding the rates of the approximations, as $\varepsilon\to0$, for $(\mathcal A^\varepsilon-\mu)^{-1}$ and $\nabla(\mathcal A^\varepsilon-\mu)^{-1}$ in the operator topology on $L_p$ for suitable~$p$. It is well-known that the rates depend on regularity of the effective operator~$\mathcal A^0$. We prove that if $(\mathcal A^0-\mu)^{-1}$ is bounded from $L_p(\Omega)^n$ to $W_p^{1+s}(\Omega)^n$ with $s\in(0,1]$, then the rates are, respectively, $\varepsilon^s$ and $\varepsilon^{s/p}$. The results are applied to the Dirichlet and Neumann problems for strongly elliptic operators with uniformly bounded and $\operatorname{VMO}$ coefficients.