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math.SP2026

Resolvent estimates for one-dimensional Dirac operators with imaginary potentials

Antonio Arnal, Tho Nguyen Duc, Petr Siegl

We investigate massive one-dimensional Dirac operators perturbed by diagonal matrix potentials of the form where the function is real-valued and unbounded at infinity. Fo…

math.SP2026

Riesz property in the case of multiple eigenvalues

Boris Mityagin, Petr Siegl

We analyze spectra and the Riesz property of spectral projections of non-symmetric perturbations of self-adjoint operators with eigenvalues having arbitrary multiplicities, includi…

math.SP2026

Revisiting the Weak Coupling Phenomenon for Two-Dimensional Schrödinger Operators

Jussi Behrndt, Petr Siegl, Nicolas Weber

We study the existence of negative eigenvalues for two-dimensional Schrödinger operators with real-valued potentials in the weak coupling regime. In his pioneering paper [Simon 19…

math.SP2025

Weak coupling for Schrödinger operators with complex potentials

Jussi Behrndt, Markus Holzmann, Petr Siegl +1

We study the discrete eigenvalues emerging from the threshold of the essential spectrum of one or two-dimensional Schrödinger operators with complex-valued -potentials in a…

math.SP2025

Generalized boundary triples for adjoint pairs with applications to non-self-adjoint Schrödinger operators

Antonio Arnal, Jussi Behrndt, Markus Holzmann +1

We extend the notion of generalized boundary triples and their Weyl functions from extension theory of symmetric operators to adjoint pairs of operators, and we provide criteria on…