Boundary homogenization of a class of obstacle problems.

We study homogenization of a boundary obstacle problem on $ C^{1,\alpha} $ domain $D$ for some elliptic equations with uniformly elliptic coefficient matrices $\gamma$. For any $ \epsilon\in\mathbb{R}_+$, $\partial D=\Gamma \cup \Sigma$, $\Gamma \cap \Sigma=\emptyset $ and $ S_{\epsilon}\subset \Sigma $ with suitable assumptions,\ we prove that as $\epsilon$ tends to zero, the energy minimizer $ u^{\epsilon} $ of $ \int_{D} |\gamma\nabla u|^{2} dx $, subject to $ u\geq \varphi $ on $ S_{\varepsilon} $, up to a subsequence, converges weakly in $ H^{1}(D) $ to $ \widetilde{u} $ which minimizes the energy functional $\int_{D}|\gamma\nabla u|^{2}+\int_{\Sigma} (u-\varphi)^{2}_{-}\mu(x) dS_{x}$, where $\mu(x)$ depends on the structure of $S_{\epsilon}$ and $ \varphi $ is any given function in $C^{\infty}(\overline{D})$.