Optimal Sobolev regularity for second order divergence elliptic operators on domains with buried boundary parts

Abstract

We study the regularity of solutions of elliptic second order boundary value problems on a bounded domain Omega in mathbbR3. The coefficients are not necessarily continuous and the boundary conditions may be mixed, i.e. Dirichlet on one part D of the boundary and Neumann on the complementing part. The peculiarity is that D is partly `buried' in Omega in the sense that the topological interior of OmegacupD properly contains Omega. The main result is that the singularity of the solution along the border of the buried contact behaves exactly as the singularity for the solution of a mixed boundary value problem along the border between the Dirichlet and the Neumann boundary part.