14 citations · 28 across the 7 of their papers we have counts for
4 papers · 1 filter
Dirac-Krein systems on star graphs
Vadym Adamyan, Heinz Langer, Christiane Tretter +1
We study the spectrum of a self-adjoint Dirac-Krein operator with potential on a compact star graph with a finite number of edges. This operator is defined by a Di…
Transfer functions and local spectral uniqueness for Sturm-Liouville operators, canonical systems and strings
Heinz Langer
It is shown that transfer functions, which play a crucial role in M.G. Krein's study of inverse spectral problems, are a proper tool to formulate local spectral uniqueness conditio…
Essential spectrum of systems of singular differential equations
Orif O. Ibrogimov, Heinz Langer, Matthias Langer +1
In this paper we develop a new method to determine the essential spectrum of coupled systems of singular differential equations. Applications to problems from magnetohydrodynamics…
Mark Krein's Method of Directing Functionals and Singular Potentials
Charles Fulton, Heinz Langer, Annemarie Luger
It is shown that M. Krein's method of directing functionals can be used to prove the existence of a scalar spectral measure for certain Sturm-Liouville equations with two singular…