8 papers
Complete Non-Selfadjointness of Extensions of Symmetric Operators with Bounded Dissipative Perturbations
Christoph Fischbacher, Andrés Felipe Patiño López, Monika Winklmeier
Using boundary triples, we develop an abstract framework to investigate the complete non-selfadjointness of the maximally dissipative extensions of dissipative operators of the for…
Maximally dissipative and self-adjoint extensions of -invariant operators
Christoph Fischbacher, Bart Rosenzweig, Jonathan Stanfill
We introduce the notion of -invariant operators, , (in a Hilbert space) with respect to a bounded and boundedly invertible operator defined via . Conditions such…
Sharp Polynomial Velocity Decay Bounds for Multidimensional Periodic Schrödinger Operators
Houssam Abdul-Rahman, Jake Fillman, Christoph Fischbacher +1
We investigate periodic Schrödinger operators in arbitrary dimensions in the large coupling regime. Our results establish that both the Lieb--Robinson velocity and the asymptotic v…
Some Remarks on the Product Formula for Defect Numbers of Closed Operators
Christoph Fischbacher, Fritz Gesztesy, Lance L. Littlejohn
This largely pedagogical paper recalls some facts on defect numbers of products of closed operators employing results from the theory of semi-Fredholm operators and then applies th…
An analysis of non-selfadjoint first-order differential operators with non-local point interactions
Christoph Fischbacher, Danie Paraiso, Chloe Povey-Rowe +1
We study the spectra of non-selfadjoint first-order operators on the interval with non-local point interactions, formally given by . We giv…
Nonnegative extensions of Sturm-Liouville operators with an application to problems with symmetric coefficient functions
Christoph Fischbacher, Jonathan Stanfill
The purpose of this paper is to study nonnegative self-adjoint extensions associated with singular Sturm-Liouville expressions with strictly positive minimal operators. We provide…