Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 4

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: essential spectrum

Sortuj według:

Ogranicz wyniki do:

Perturbation theory, M-essential spectra of 2 x 2 operator matrices and application to transport operators

Jeribi Aref, Moalla Nedra, Yengui Sonia

Journal of Mathematics and Applications

2021

Vol. 44

35--55

In this article we give some results on perturbation theory of 2 x 2 block operator matrices on the product of Banach spaces. Furthermore, we investigate their M-essential spectra. Finally, we apply the obtained results to determine the M-essential spectra of two group transport operators with general boundary conditions in the Banach space Lp([-a, a] x [-1, 1]) x Lp([-a, a] x [-1, 1]), p ≥ 1 and a > 0.

On the spectrum of periodic perturbations of certain unbounded Jacobi operators

Sahbani J.

Opuscula Mathematica

2016

Vol. 36, no. 6

807--818

It is known that a purely off-diagonal Jacobi operator with coefficients [formula] has a purely absolutely continuous spectrum filling the whole real axis. We show that a 2-periodic perturbation of these operators creates a non trivial gap in the spectrum.

Hildebrandt's theorem for the essential spectrum

Bracic J., Diogo C.

Opuscula Mathematica

2015

Vol. 35, no. 3

279--285

We prove a variant of Hildebrandt's theorem which asserts that the convex hull of the essential spectrum of an operator A on a complex Hilbert space is equal to the intersection of the essential numerical ranges of operators which are similar to A. As a consequence, it is given a necessary and sufficient condition for zero not being in the convex hull of the essential spectrum of A.

A note on the discrete Schrodinger operator with a perturbed periodic potential

Strack B.

Opuscula Mathematica

2010

Vol. 30, no. 2

193-202

The aim of this paper is to study the spectrum of the one-dimensional discrete Schrödinger operator with a perturbed periodic potential. We obtain natural conditions under which this perturbation preserves the essential spectrum of the considered operator. Conditions on the number of isolated eigenvalues are given.