Finite Rank Perturbations, Scattering Matrices and Inverse Problems

In this paper the scattering matrix of a scattering system consisting of two selfadjoint operators with finite-dimensional resolvent difference is expressed in terms of a matrix Nevanlinna function. The problem is embedded into an extension theoretic framework and the theory of boundary triplets and associated Weyl functions for (in general nondensely defined) symmetric operators is applied. The representation results are extended to dissipative scattering systems and an explicit solution of an inverse scattering problem for the Lax-Phillips scattering matrix is presented