Weyl theory for Dirac systems with rectangular matrix potentials is non-classical. The corresponding Weyl functions are rectangular matrix functions. Furthermore, they are non-expansive in the upper semi-plane. Inverse problems are treated for such Weyl functions, and some results are new even for the square Weyl functions. High energy asymptotics of Weyl functions and Borg-Marchenko type uniqueness results are derived too.
@article{arxiv.1106.1263,
title = {Recovery of Dirac system from the rectangular Weyl matrix function},
author = {B. Fritzsche and B. Kirstein and I. Ya. Roitberg and A. L. Sakhnovich},
journal= {arXiv preprint arXiv:1106.1263},
year = {2015}
}