227 citations · 812 across the 43 of their papers we have counts for
5 papers · 1 filter
On the Hamiltonian-Krein index for a non-self-adjoint spectral problem
Aleksey Kostenko, Noema Nicolussi
We investigate the instability index of the spectral problem on the line , where is rea…
Spectral Estimates for Infinite Quantum Graphs
Aleksey Kostenko, Noema Nicolussi
We investigate the bottom of the spectra of infinite quantum graphs, i.e., Laplace operators on metric graphs having infinitely many edges and vertices. We introduce a new definiti…
The Classical Moment Problem and Generalized Indefinite Strings
Jonathan Eckhardt, Aleksey Kostenko
We show that the classical Hamburger moment problem can be included in the spectral theory of generalized indefinite strings. Namely, we introduce the class of Krein-Langer strings…
Spectral Theory of Infinite Quantum Graphs
Pavel Exner, Aleksey Kostenko, Mark Malamud +1
We investigate quantum graphs with infinitely many vertices and edges without the common restriction on the geometry of the underlying metric graph that there is a positive lower b…
The Camassa--Holm Equation and The String Density Problem
Jonathan Eckhardt, Aleksey Kostenko, Gerald Teschl
In this paper we review the recent progress in the (indefinite) string density problem and its applications to the Camassa--Holm equation.