We consider the symmetric FEM-BEM coupling for the numerical solution of a (nonlinear)
interface problem for the 2D Laplacian. We introduce some new a posteriori
error estimators based on the (h − h/2)-error
estimation strategy. In particular, these include the approximation error for the boundary
data, which allows to work with discrete boundary integral operators only. Using the
concept of estimator reduction, we prove that the proposed adaptive algorithm is
convergent in the sense that it drives the underlying error estimator to zero. Numerical
experiments underline the reliability and efficiency of the considered adaptive
mesh-refinement.