The concepts of boundary relations and the corresponding Weyl families are introduced. Let
$ S $ be a closed symmetric linear operator or, more generally, a closed symmetric relation …

Motivated by the study of certain nonlinear wave equations (in particular, the Camassa–
Holm equation), we introduce a new class of generalized indefinite strings associated with …

On Weyl–Titchmarsh theory for singular finite difference Hamiltonian systems - ScienceDirect
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We give a dynamical characterization of measures on the real line with finite logarithmic
integral. The general case is considered in the setting of evolution groups generated by de …

This paper is concerned with a class of discrete linear Hamiltonian systems in finite or
infinite intervals. A definiteness condition and its equivalent statements are discussed and …

One of the central objects in the theory of singular Sturm-Liouville differential expressions is
the Titchmarsh-Weyl function m introduced and studied in the classical works of Titchmarsh …

The Schrödinger equation with a potential periodically varying in time is used to model
adiabatic quantum pumps. The systems considered may be either infinitely extended and …

We extend a result on renormalized oscillation theory, originally derived for Sturm–Liouville
and Dirac-type operators on arbitrary intervals in the context of scalar coefficients, to the …

We use the Dirac equation in a fixed black hole background and different independent
techniques to demonstrate the absence of fermionic bound states around a Schwarzschild …

Building on work on Miura's transformation by Kappeler, Perry, Shubin, and Topalov, we
develop a detailed spectral theoretic treatment of Schrödinger operators with matrix-valued …