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I present an example of a discrete Schr"odinger operator that shows that it is possible to have embedded singular spectrum and, at the same time, discrete eigenvalues that approach the edges of the essential spectrum (much) faster than…

Spectral Theory · Mathematics 2015-06-26 Christian Remling

We consider Schr\"odinger operators on sparse graphs. The geometric definition of sparseness turn out to be equivalent to a functional inequality for the Laplacian. In consequence, sparseness has in turn strong spectral and functional…

Spectral Theory · Mathematics 2014-02-07 Michel Bonnefont , Sylvain Golenia , Matthias Keller

We prove eigenvalue bounds for Schr\"odinger operator $-\Delta_g+V$ on compact manifolds with complex potentials $V$. The bounds depend only on an $L^q$-norm of the potential, and they are shown to be optimal, in a certain sense, on the…

Spectral Theory · Mathematics 2025-10-28 Jean-Claude Cuenin

In this note we provide an explicit lower bound on the spectral gap of one-dimensional Schr\"odinger operators with non-negative bounded potentials and subject to Neumann boundary conditions.

Spectral Theory · Mathematics 2022-10-13 Joachim Kerner

Using an extension of the H\"ormander product of distributions, we obtain an intrinsic formulation of one-dimensional Schr\"odinger operators with singular potentials. This formulation is entirely defined in terms of standard {\it Schwartz}…

Spectral Theory · Mathematics 2018-07-17 Nuno Costa Dias , Joao Nuno Prata , Cristina Jorge

In this paper we continue the study of the spectral gap of Schr\"odinger operators on large intervals and subject to Neumann boundary conditions. The main goal is to derive a lower bound on the spectral gap which is polynomial in the…

Spectral Theory · Mathematics 2022-10-13 Joachim Kerner

The purpose of this article is to study pseudospectral properties of the one-dimensional Schr\"{o}dinger operator perturbed by a complex steplike potential. By constructing the resolvent kernel, we show that the pseudospectrum of this…

Spectral Theory · Mathematics 2023-10-24 Tho Nguyen Duc

We prove upper bounds on the number of resonances and eigenvalues of Schr\"odinger operators $-\Delta+V$ with complex-valued potentials, where $d\geq 3$ is odd. The novel feature of our upper bounds is that they are \emph{effective}, in the…

Spectral Theory · Mathematics 2024-11-22 Jean-Claude Cuenin

We extend a result of Davies and Nath on the location of eigenvalues of Schr\"odinger operators with slowly decaying complex-valued potentials to higher dimensions. In this context, we also discuss various examples related to the…

Spectral Theory · Mathematics 2019-11-27 Jean-Claude Cuenin

This note points out some bounds for the number of negative eigenvalues of Schroedinger operators with Hardy-type potentials, which follow from a simple coordinate transformation, and could prove useful in a spectral analysis of certain…

Mathematical Physics · Physics 2009-11-18 Douglas Lundholm

In a first part of this paper we investigate the continuity (stability) of the spectrum of a class of non-local Schr\"odinger operators on varying the potentials. By imposing conditions of different strength on the convergence of the…

Analysis of PDEs · Mathematics 2022-11-21 Giacomo Ascione , József Lőrinczi

We consider eigenvalue sums of Schr\"odinger operators $-\Delta+V$ on $L^2(\R^d)$ with complex radial potentials $V\in L^q(\R^d)$, $q<d$. We prove quantitative bounds on the distribution of the eigenvlaues in terms of the $L^q$ norm of $V$.…

Spectral Theory · Mathematics 2024-09-06 Jean-Claude Cuenin , Solomon Keedle-Isack

We consider Schr\"odinger operators with periodic potentials in the positive quadrant for dim $>1$ with Dirichlet boundary condition. We show that for any integer $N$ and any interval $I$ there exists a periodic potential such that the…

Spectral Theory · Mathematics 2017-12-27 Evgeny Korotyaev , Jacob Schach Moller

We consider the Schr\"odinger operator in the plane with delta-potential supported by a curve. For the cases of an infinite curve and a finite loop we give estimates on the lower bound of the spectrum expressed explicitly through the…

Spectral Theory · Mathematics 2010-11-11 Igor Lobanov , Vladimir Lotoreichik , Igor Popov

We study the effect of non-negative potentials on the spectral gap of one-dimensional Schr\"odinger operators in the limit of large intervals. In particular, we derive upper and lower bounds on the gap for different classes of potentials…

Spectral Theory · Mathematics 2024-11-05 Joachim Kerner , Matthias Täufer

We consider Schr\"odinger operators with complex-valued decreasing potentials on the half-line. Such operator has essential spectrum on the half-line plus eigenvalues (counted with algebraic multiplicity) in the complex plane without the…

Mathematical Physics · Physics 2019-10-02 Evgeny Korotyaev

We prove that the eigenvalues of a continuum random Schr\"odinger operator $-\Delta+ V_{\omega}$ of Anderson type, with complex decaying potential, can be bounded (with high probability) in terms of an $L^q$ norm of the potential for all…

Spectral Theory · Mathematics 2025-02-12 Jean-Claude Cuenin , Konstantin Merz

The discrete one-dimensional Schr\"odinger operator is studied in the finite interval of length $N=2 M$ with the Dirichlet boundary conditions and an arbitrary potential even with respect to the spacial reflections. It is shown, that the…

Mathematical Physics · Physics 2014-04-18 Sergei B. Rutkevich

We review some results and proofs on eigenvalue bounds for random Schr\"odinger operators with complex-valued potentials. We also include new Schatten norm estimates for the resolvent and use them to obtain bounds for sums of eigenvalues.

Spectral Theory · Mathematics 2023-08-29 Jean-Claude Cuenin , Konstantin Merz

We prove exponential and dynamical localization for the Schr\"odinger operator with a nonnegative Poisson random potential at the bottom of the spectrum in any dimension. We also conclude that the eigenvalues in that spectral region of…

Mathematical Physics · Physics 2007-05-23 François Germinet , Peter D. Hislop , Abel Klein