7 papers
A growth estimate for the monodromy matrix of a canonical system
Raphael Pruckner, Harald Woracek
We investigate the spectrum of 2-dimensional canonical systems in the limit circle case. It is discrete and, by the Krein-de Branges formula, cannot be more dense than the integers…
Nawrotzki's Algorithm for the Countable Splitting Lemma, Constructively
Ana Sokolova, Harald Woracek
We reprove the countable splitting lemma by adapting Nawrotzki's algorithm which produces a sequence that converges to a solution. Our algorithm combines Nawrotzki's approach with…
Limit behaviour of Weyl coefficients
Raphael Pruckner, Harald Woracek
We study the sets of radial or nontangential limit points towards of a Nevanlinna function q. Given a nonempty, closed, and connected subset L of , we explicitly co…
Canonical systems with discrete spectrum
Roman Romanov, Harald Woracek
We study spectral properties of two-dimensional canonical systems , , where the Hamiltonian is locally integrable on , positive semidefinite…
Proper Semirings and Proper Convex Functors
Ana Sokolova, Harald Woracek
Esik and Maletti introduced the notion of a proper semiring and proved that some important (classes of) semirings -- Noetherian semirings, natural numbers -- are proper. Properness…
Spectral multiplicity of selfadjoint Schroedinger operators on star-graphs with standard interface conditions
Sergey Simonov, Harald Woracek
We analyze the singular spectrum of selfadjoint operators which arise from pasting a finite number of boundary relations with a standard interface condition. A model example for th…