### $\mathit{A}$-$\mathrm{\mathit{P}\mathit{O}\mathit{S}\mathit{T}\mathit{E}\mathit{R}\mathit{I}\mathit{O}\mathit{R}\mathit{I}}$ error estimates for linear exterior problems $\mathrm{\mathit{V}\mathit{I}\mathit{A}}$ mixed-FEM and DtN mappings

In this paper we combine the dual-mixed finite element method with a Dirichlet-to-Neumann mapping (given in terms of a boundary integral operator) to solve linear exterior transmission problems in the plane. As a model we consider a second order elliptic equation in divergence form coupled with the Laplace equation in the exterior unbounded region. We show that the resulting mixed variational formulation and an associated discrete scheme using Raviart-Thomas spaces are well posed, and derive the...