It is shown that the nonselfadjoint (and non-normal) linear ordinary differential operators of a certain class are spectral operators of scalar type in the sense of Dunford and Bade. Operators of this kind appear in physical problems such as the scattering of spin waves by magnetic solitons.
Let $(λ_-,λ_+)$ be a spectral gap of a periodic Schrödinger operator $A$ on the lattice ${\mathbb Z}^d$. Consider the operator $A(α)=A-αV$ where $V$ is a decaying positive potential on ${\mathbb Z}^d$. We study the asymptotic behavior of the number of eigenvalues of $A(t)$ passing through a point $λ\in (λ_-,λ_+)$ as $t$ grows from $0$ to $α$.
We consider the graphene operator $D_m$ perturbed by a decaying potential $αV$, where $α$ is a coupling constant. We study the number $N(λ,α)$ of eigenvalues of the operator $D(t)=D_m-tV$ passing through a regular point $λ\inρ(D_m)$ as $t$ changes from $0$ to $α$. We obtain asymptotic formulas for $N(λ,α)$ as $α\to\infty$.
In this paper we consider the Bloch eigenvalues and spectrum of the non-self-adjoint differential operator L generated by the differential expression of odd order n with the periodic PT-symmetric coefficients, where n>1. We study the localizations of the Bloch eigenvalues and the structure of the spectrum. Moreover, we find conditions on the norm of the coefficients under which the spectrum of L coincides with the real line
This is a pedagogic introduction to certain aspects of inverse spectral theory for Schrödinger operators and Jacobi matrices that revolves around my joint work with Fritz Gesztesy whose $70^{th}$ birthday we are honoring.
ABSTRACT This research aimed to investigate the occurrence of Chlamydia sp., Morbillivirus sp., Parvovirus sp., Leishmania sp. and Alphacoronavirus sp. in captive giant anteaters. Blood and fecal samples were taken from 16 animals in institutions from the states of Minas Gerais, Bahia and Distrito Federal, which had been in captivity for at least a year. A commercial rapid chromatographic immunoassay test was used for detecting coronavirus and parvovirus antigens, in addition to antibodies against leishmaniasis, all results being negative. In the case of the test for antibodies against distemper, four (4/16; 25%) anteaters had an average titration, two (2/16; 12.5%) a low titration and ten (10/16; 62.5%) were non-reactive. Using the DOT-ELISA (dot blotting) method for detection of immunoglobulin G, only one specimen obtained a 1 : 40 titration. For the polymerase chain reaction tests for Leishmania and Chlamydia, all samples were negative.
We study the ground state energy of the Neumann magnetic Laplacian on planar domains. For a constant magnetic field we consider the question whether, under an assumption of fixed area, the disc maximizes this eigenvalue. More generally, we discuss old and new bounds obtained on this problem.
In this paper, we study the non-self dual extended Harper's model with Liouvillean frequency. By establishing quantitative reducibility results together with the averaging method, we prove that the lengths of spectral gaps decay exponentially.
In this paper, we give Lieb-Thirring type inequalities for isolated eigenvalues of $d$-dimensional non-selfadjoint Schrödinger operators with complex-valued and dilation analytic potentials. In order to derive them, we prove that isolated eigenvalues and their multiplicities are invariant under complex dilation.
We prove that the optimal constant in the Lieb--Thirring inequality on a star graph with $N$ edges coincides with that on $\mathbb R$ if $N$ is even. For odd $N$ we show that this property holds when restricting to radial potentials and we prove an almost optimal bound for general potentials.
We establish a partial generalization of a prior isoperimetric inequality for the fundamental tone (first nonzero eigenvalue) of the free plate to plates of nonzero Poisson's ratio.
With the help of the representation of SL(2,Z) on the rank two free module over the integer adeles, we define the transition operator of a Markov chain. The real component of its spectrum exhibits a gap, whereas the non-real component forms a circle of radius 1/\sqrt{2}.
This paper is concerned with the lower bounds for the principal frequency of the $p$-Laplacian on $n$-dimensional Euclidean domains. In particular, we extend the classical results involving the inner radius of a domain and the first eigenvalue of the Laplace operator to the case $p\neq2$. As a by-product, we obtain a lower bound on the size of the nodal set of an eigenfunction of the $p$-Laplacian on planar domains.
In this paper we investigate the one-dimensional Schrodinger operator L(q) with complex-valued periodic potential q when q\inL_{1}[0,1] and q_{n}=0 for n=0,-1,-2,..., where q_{n} are the Fourier coefficients of q with respect to the system {e^{i2πnx}}. We prove that the Bloch eigenvalues are (2πn+t)^{2} for n\inZ, t\inC and find explicit formulas for the Bloch functions. Then we consider the inverse problem for this operator.
In this note, we present a generalization of some results concerning the spectral properties of a certain class of block matrices. As applications, we study some of its implications on nonnegative matrices, doubly stochastic matrices and graph theory namely on graph spectra and graph energy.
Assuming the negative part of the potential is uniformly locally $L^1$, we prove a pointwise $L^p$ estimate on derivatives of eigenfunctions of one-dimensional Schrodinger operators. In particular, if an eigenfunction is in $L^p$, then so is its derivative, for $1\le p\le \infty$.
Asymptotics of the ground state energy of the heavy atoms and molecules in the self-generated magnetic field has been derived and for minimal energy positions of nuclei remainder estimate $O(N^{16/9})$ has been recovered.
We prove that the number of negative eigenvalues of two-dimensional magnetic Schroedinger operators is bounded from above by the strength of the corresponding electric potential. Such estimates fail in the absence of a magnetic field. We also show how the corresponding upper bounds depend on the properties of the magnetic field and discuss their connection with Hardy-type inequalities.
We obtain asymptotic formulas for eigenvalues and eigenfunctions of the operator generated by a system of ordinary differential equations with summable coefficients and periodic or antiperiodic boundary conditions. Then using these asymptotic formulas, we find necessary and sufficient conditions on the coefficients for which the system of eigenfunctions and associated functions of the operator under consideration forms a Riesz basis.