Results 31 to 40 of about 1,201 (92)
Local spectral theory for 2 × 2 operator matrices
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 42, Page 2667-2672, 2003., 2003 We discuss the spectral properties of the operator MC ∈ ℒ(X ⊕ Y) defined by MC:=(AC0B), where A ∈ ℒ(X), B ∈ ℒ(Y), C ∈ ℒ(Y, X), and X, Y are complex Banach spaces. We prove that (SA∗∩SB)∪σ(MC)=σ(A)∪σ(B) for all C ∈ ℒ(Y, X). This allows us to give a partial positive answer to Question 3 of Du and Jin (1994) and generalizations of some results of Houimdi ...
H. Elbjaoui, E. H. Zerouali
wiley +1 more source
Sequences of bounds for the spectral radius of a positive operator
, 2019 In 1992, Szyld provided a sequence of lower bounds for the spectral radius of a nonnegative matrix $A$, based on the geometric symmetrization of powers of $A$.
Drnovšek, Roman
core +1 more source
Spectral inclusions and stability results for strongly continuous semigroups
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 37, Page 2379-2387, 2003., 2003 We prove some spectral inclusions for strongly continuous semigroups. Some stability results are also established.
Abdelkader Elkoutri, Mohamed Aziz Taoudi
wiley +1 more source
On the continuity of spectra for families of magnetic pseudodifferential operators
, 2010 For families of magnetic pseudodifferential operators defined by symbols and magnetic fields depending continuously on a real parameter $\epsilon$, we show that the corresponding family of spectra also varies continuously with $\epsilon$.Comment: 22 ...
Blanchard E. +5 more
core +2 more sources
The spectrum of a class of almost periodic operators
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 36, Page 2277-2301, 2003., 2003 For almost Mathieu operators, it is shown that the occurrence of Cantor spectrum and the existence, for every point in the spectrum and suitable phase parameters, of at least one localized eigenfunction which decays exponentially are inconsistent properties.
Norbert Riedel
wiley +1 more source
On the largest analytic set for cyclic operators
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 30, Page 1899-1909, 2003., 2003 We describe the set of analytic bounded point evaluations for an arbitrary cyclic bounded linear operator T on a Hilbert space ℋ; some related consequences are discussed. Furthermore, we show that two densely similar cyclic Banach‐space operators possessing Bishop′s property (β) have equal approximate point spectra.
A. Bourhim
wiley +1 more source
Open Mathematics, 2020 In this paper, we describe a method to solve the problem of finding periodic solutions for second-order neutral delay-differential equations with piecewise constant arguments of the form x″(t) + px″(t − 1) = qx([t]) + f(t), where [⋅] denotes the greatest
I. Muminov Mukhiddin, H. M. Murid Ali
doaj +1 more source
Common fixed point theorems for a pair of countably condensing mappings in ordered banach spaces
International Journal of Stochastic Analysis, Volume 16, Issue 3, Page 243-248, 2003., 2003 In this paper some common fixed point theorems for a pair of multivalued weakly isotone mappings on an ordered Banach space are proved.
B. C. Dhage +2 more
wiley +1 more source
On a class of $h$-Fourier integral operators
, 2013 In this paper, we study the $L^{2}$-boundedness and $L^{2}$-compactness of a class of $h$-Fourier integral operators. These operators are bounded (respectively compact) if the weight of the amplitude is bounded (respectively tends to $0)$
Abderrahmane, Senoussaoui +1 more
core +2 more sources
The Property (EA) and Local Spectral Theory
International Journal of Mathematics and Mathematical Sciences, Volume 2025, Issue 1, 2025.In this paper, we introduce and study the spectral property (EA). This property means that the difference between the approximate point spectrum and the upper semi‐Fredholm spectrum coincides with the difference between the approximate point spectrum and the upper semi‐Weyl spectrum.
Elvis Aponte +3 more
wiley +1 more source