A symmetric Nevanlinna function Q is of the form Q (z)= zQs (z2) where Qs and Q 0 (z)= zQs
(z) are also Nevanlinna functions. In such a situation Qs and–Q–10 are Stieltjes functions …

The subject of this survey is to review the basics of Louis de Branges' theory of Hilbert
spaces of entire functions, and to present results bringing together the notions of de Branges …

A canonical differential equation is a system y′= zJHy with a real, nonnegative and locally
integrable 2× 2-matrix valued function H. The theory of a canonical system is closely related …

In the theory of two-dimensional canonical (also called 'Hamiltonian') systems, the notion of
the Titchmarsh-Weyl coefficient associated to a Hamiltonian function plays a vital role. A …

We investigate a particular subclass of so-called symmetric indefinite Hermite-Biehler
functions and give a characterization of functions of this class in terms of the location of their …

We introduce an indefinite analogue of the so-called Stieltjes class and provide some basic
results on this indefinite Stieltjes class. Among them: The relation between the functions q …

We consider a Hamiltonian system of the form y (x)= jh (x) y (x), with a locally integrable and
nonnegative 2 x 2-matrix-valued Hamiltonian (H). I n the literature dealing with the operator …

The subclasses N κ (∞) of the classes N κ of generalized Nevanlinna functions appear in
the context of Pontryagin space models, where they correspond to model relations having a …

The growth properties of de Branges spaces and their subspaces are studied. It is shown
that, for each given pair of growth functions $\lambda (r)= O (r) $ and $\lambda _1= o …

We study two-dimensional Hamiltonian systems of the form (*) where the Hamiltonian H is
locally integrable on [s-, s+) and nonnegative, and. The spectral theory of the equation …