Results 41 to 50 of about 499 (74)
On the numerical range of a generalized derivation
, 2017 We examine the relationship between the numerical range of the restriction of a generalized derivation to a norm ideal J and that of its implementing elements.
F. M. Runji, J. O. Agure, F. Nyamwala
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On Berezin norm and Berezin number inequalities for sum of operators
Demonstratio MathematicaThe aim of this study is to obtain several inequalities involving the Berezin number and the Berezin norm for various combinations of operators acting on a reproducing kernel Hilbert space.
Altwaijry Najla +2 more
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Convexity around the Unit of a Banach Algebra [PDF]
, 2008 2000 Mathematics Subject Classification: Primary: 46B20. Secondary: 46H99, 47A12.We estimate the (midpoint) modulus of convexity at the unit 1 of a Banach algebra A showing that inf {max±||1 ± x|| − 1 : x ∈ A, ||x||=ε} ≥ (π/4e)ε²+o(ε²) as ε → 0. We also
Kadets, Vladimir +3 more
core
Operator radii and unitary operators
, 2010 Let ρ 1 and wρ(A) be the operator radius of a linear operator A . Suppose m is a positive integer. It is shown that for a given invertible linear operator A acting on a Hilbert space, one has wρ (A−m) wρ (A)−m .
T. Andô, Chi-Kwong Li
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Crouzeix's conjecture, compressions of shifts, and classes of nilpotent matrices
Concrete OperatorsThis article studies the level set Crouzeix (LSC) conjecture, which is a weak version of Crouzeix’s conjecture that applies to finite compressions of the shift.
Bickel Kelly +4 more
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Algebraic properties of the set of operators with 0 in the closure of the numerical range
, 2013 Sets of operators which have zero in the closure of the numerical range are studied. For some particular sets T ⊆B(H ) , we characterize the set of all operators A ∈B(H ) such that 0 ∈W(TA) for every T ∈ T .
C. Diogo
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Weakly selfadjoint operators II [PDF]
, 2009 In this note, we show some basic results related to the spectrum of a weakly selfadjoint ...
Nakamura Noboru
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Generalized finite operators and orthogonality
SUT Journal of Mathematics, 2011 In this paper we prove that a spectraloid operator is finite, we present some generalized finite operators and we give a new class of finite op- erators. Also, the orthogonality of some operators is studied.
S. Bouzenada
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Matrices with defect index one
, 2013 In this paper, we give some characterizations of matrices which have defect index one. Recall that an n -by-n matrix A is said to be of class Sn (resp., S −1 n ) if its eigenvalues are all in the open unit disc (resp., in the complement of closed unit ...
Cheng Chang +4 more
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, 2002 There exist operators $A$ such that : for any sequence of contractions $\{A_n\}$, there is a total sequence of mutually orthogonal projections $\{E_n\}$ such that $\Sigma E_nAE_n=\bigoplus A_n$.Comment: 11 ...
Bourin, Jean-Christophe
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