Results 61 to 70 of about 1,449 (134)
Journal of Mathematics, Volume 2025, Issue 1, 2025.This paper investigates an abstract nonhomogeneous backward Cauchy problem governed by an unbounded linear operator in a Hilbert space H. The coefficient operator in the equation is assumed to be unbounded, self‐adjoint, positive, and to possess a discrete spectrum, with data prescribed at the final time t = T.
Nihed Teniou, Xian-Ming Gu
wiley +1 more source
On some properties of Banach operators
International Journal of Mathematics and Mathematical Sciences, Volume 27, Issue 3, Page 149-153, 2001., 2001 A mapping α from a normed space X into itself is called a Banach operator if there is a constant k such that 0 ≤ k < 1 and ‖α2(x) − α(x)‖ ≤ k‖α(x) − x‖ for all x ∈ X. In this note we study some properties of Banach operators. Among other results we show that if α is a linear Banach operator on a normed space X, then N(α − 1) = N((α−1)2), N(α − 1)∩R(α −
A. B. Thaheem, AbdulRahim Khan
wiley +1 more source
Topological properties of the block numerical range of operator matrices
, 2020 We show that the block numerical range of an n×n -operator matrix A corresponding to an operator A on the Banach space X with respect to a decomposition X = ∏Xj has at most n connected components.
Agnes Radl, M. Wolff
semanticscholar +1 more source
On the spectrum of ψ‐contracting operators
International Journal of Stochastic Analysis, Volume 14, Issue 3, Page 303-308, 2001., 2001 The spectrum σ(A) of a continuous linear operator A : E → E defined on a Banach space E, which is contracting with respect to the Hausdorff measure of noncompactness, is investigated.
Anwar A. Al-Nayef
wiley +1 more source
On the generalized Kato spectrum [PDF]
, 2011 2010 Mathematics Subject Classification: 47A10.We show that the symmetric difference between the generalized Kato spectrum and the essential spectrum defined in [7] by sec(T) = {l О C ; R(lI-T) is not closed } is at most countable and we also give some
Benharrat, Mohammed, Messirdi, Bekkai
core
Operators with minimal pseudospectra and connections to normality
, 2020 This paper mainly studies the class of bounded linear operators A with minimal pseudospectra σε (A) = σ(A)+Dε for some ε > 0 , where σ(A) denotes the spectrum of A , and Dε denotes the open disk of radius ε centered at the origin.
Samir Raouafi
semanticscholar +1 more source
Additive spectra of the 1/4 Cantor measure [PDF]
, 2013 In this paper, we add to the characterization of the Fourier spectra for Bernoulli convolution measures. These measures are supported on Cantor subsets of the line.
Jorgensen, Palle E. T. +2 more
core
The Resolvent of Impulsive Singular Hahn–Sturm–Liouville Operators
Annales Mathematicae SilesianaeIn this study, the resolvent of the impulsive singular Hahn–Sturm– Liouville operator is considered. An integral representation for the resolvent of this operator is obtained.
Allahverdiev Bilender P. +2 more
doaj +1 more source
Spectral isometries on non-simple C*-algebras [PDF]
, 2011 We prove that unital surjective spectral isometries on certain non-simple unital C*-algebras are Jordan isomorphisms. Along the way, we establish several general facts in the setting of semisimple Banach algebras.Comment: 7 pages; paper available since ...
Ahmed, Martin Mathieu, R. Sourour
core
Essential spectrum of a fermionic quantum field model
, 2014 An interaction system of a fermionic quantum field is considered. The state space is defined by a tensor product space of a fermion Fock space and a Hilbert space. It is assumed that the total Hamiltonian is a self-adjoint operator on the state space and
Takaesu, Toshimitsu
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