One of our main goals in this talk is to overview developments in spectral theory of generalized indefinite stings, the object introduced by J. Eckhardt and the speaker almost 10 years ago. In particular, we plan to present a characterization of spectral measures/Weyl-Titchmarsh functions of (relative) Hilbert-Schmidt perturbations of some model strings. Our second goal is to demonstrate the application of this result to the conservative Camassa-Holm flow, for which generalized indefinite strings serve as Lax (isospectral) operators.
Based on joint work with J. Eckhardt (Loughborough).