Self-adjoint Schrödinger operators with δ and δ′-potentials supported on a smooth
compact hypersurface are defined explicitly via boundary conditions. The spectral properties …

The concept of quasi boundary triples and Weyl functions from extension theory of
symmetric operators in Hilbert spaces is developed further and spectral estimates for …

Singular Green operators G appear typically as boundary correction terms in resolvents for
elliptic boundary value problems on a domain Ω⊂ ℝ n, and more generally they appear in …

For a second-order symmetric strongly elliptic operator A on a smooth bounded open set in
R n, the mixed problem is defined by a Neumann-type condition on a part Σ+ of the …

The spectral behavior of the difference between the resolvents of two realizations zA1 and
zA2 of a second-order strongly elliptic symmetric differential operator A, defined by different …

For selfadjoint extensions A˜ of a symmetric densely defined positive operator Amin, the
lower boundedness problem is the question of whether A˜ is lower bounded if and only if an …

This is a short survey on the connection between general extension theories and the study
of realizations of elliptic operators A on smooth domains in R^ n, n> 1. The theory of …

We discuss the detectable subspaces of an operator. We analyse the relation between the M-
function (the abstract Dirichlet to Neumann map) and the resolvent bordered by projections …

In the present thesis a unified functional analytic approach to the treatment of self-adjoint
elliptic operators with Dirichlet, Neumann, Robin, and more general self-adjoint boundary …

Partial differential equations and corresponding boundary value problems appear in the
modeling of numerous processes in science and engineering. Many mathematical models …