Quantum scattering from arbitrary boundaries

We present a conceptually and numerically simple method for obtaining scattering eigenstates from arbitrary disconnected open or closed boundaries with very general boundary conditions. As a side effect of the derivation, a solution for partially penetrable walls is also found. As in the boundary integral Green-function method, an integral equation over the boundary results: however, our approach uses delta-function potentials which can have finite or infinite strength) to enforce boundary conditions and construct the governing equations: rather than Green's theorem.