Results 31 to 40 of about 694 (64)

Inequalities for eigenvalues of compactly perturbed unitary operators

, 2017
We consider the operator A = U +K , where U is a unitary operator and K is a compact one. An eigenvalue λ of A is said to be a non-unitary one, if |λ | = 1 . We derive inequalities for sums of absolute values of the non-unitary eigenvalues.
M. Gil'
semanticscholar   +1 more source

On the stability of self-adjointness of linear relations

, 2019
This paper focuses on the stability of self-adjointness of linear relations under perturbations in Hilbert spaces. It is shown that a self-adjoint relation is still self-adjoint under bounded and relatively bounded perturbations.
Liu, Yan
core   +1 more source

Nilpotent perturbations of m-isometric and m-symmetric tensor products of commuting d-tuples of operators

Demonstratio Mathematica
If T1{{\mathbb{T}}}_{1} and T2{{\mathbb{T}}}_{2} are commuting dd-tuples of Hilbert space operators in B(ℋ)dB{\left({\mathcal{ {\mathcal H} }})}^{d} such that (T1*⊗I+I⊗T2*,T1⊗I+I⊗T2)\left({{\mathbb{T}}}_{1}^{* }\otimes I+I\otimes {{\mathbb{T}}}_{2}^{* },{
Duggal Bhagwati Prashad, Kim In Hyoun
doaj   +1 more source

Taylor approximations of operator functions

, 2013
This survey on approximations of perturbed operator functions addresses recent advances and some of the successful methods.Comment: 12 ...
A Skripka, A Skripka, A Skripka, A Skripka, AB Aleksandrov, AH Chamseddine, AV Rybkin, D Potapov, D Potapov, D Potapov, D Potapov, D Potapov, DR Yafaev, E Kissin, F Gesztesy, H Neidhardt, J-M Bouclet, K Dykema, K Dykema, MG Krein, MG Krein, MS Birman, MS Birman, NA Azamov, NA Azamov, NA Azamov, RW Carey, S Lord, VM Adamjan, VV Peller, WD Suijlekom van, YB Farforovskaya, YB Farforovskaya, YB Farforovskaya, YL Daleckii   +34 more
core   +1 more source

Quantitative bounds on the discrete spectrum of non self-adjoint quantum magnetic Hamiltonians [PDF]

, 2016
We establish Lieb-Thirring type inequalities for non self-adjoint relatively compact perturbations of certain operators of mathematical physics. We apply our results to quantum Hamiltonians of Schr{\"o}dinger and Pauli with constant magnetic field of ...
Sambou, Diomba
core  

Point Interactions: PT-Hermiticity and Reality of the Spectrum

, 2002
General point interactions for the second derivative operator in one dimension are studied. In particular, ${\mathcal P \mathcal T}$-self-adjoint point interactions with the support at the origin and at points $\pm l$ are considered. The spectrum of such
Albeverio, S., Fei, S. M., Kurasov, P.
core   +1 more source

Essential spectra of some matrix operators by means of measures of weak noncompactness

, 2014
In this paper, we give some results concerning stability in the Fredholm theory via the concept of measures of weak noncompactness. These results are exploited to investigate the essential spectra of some matrix operators on Banach spaces.
Boulbeba Abdelmoumen
semanticscholar   +1 more source

Rank-one perturbations of normal operators and hyponormality

, 2014
Let T = N + u⊗ v be a rank-one perturbation of a normal operator N acting on a separable, infinite dimensional, complex Hilbert space H . It is proved that the hyponormality of T is equivalent to the normality of T .
I. Jung, Eun-young Lee
semanticscholar   +1 more source

Variation of discrete spectra for non-selfadjoint perturbations of selfadjoint operators

, 2013
Let B=A+K where A is a bounded selfadjoint operator and K is an element of the von Neumann-Schatten ideal S_p with p>1. Let {\lambda_n} denote an enumeration of the discrete spectrum of B.
E.B. Davies, I.C. Gohberg, L. Golinskii, M. Hansmann, M. Hansmann, M. Hansmann, M.I. Gil’, Marcel Hansmann, P. The Lai, R. Bhatia, R. Bhatia, R. Bhatia, R. Bhatia, R. Bouldin, T. Kato, V.I. Macaev, W. Kahan   +16 more
core   +1 more source

Exponential decay of eigenfunctions of first order systems

, 2007
For first order systems, we obtain an efficient bound on the exponential decay of an eigenfunction in terms of the distance between the corresponding eigenvalue and the essential spectrum.
Yafaev, D. R.
core   +3 more sources