Results 51 to 60 of about 865 (99)
, 2012 The $k$-rank numerical range $\Lambda_{k}(A)$ is expressed via an intersection of a countable family of numerical ranges $\{F(M^{*}_{\nu}AM_{\nu})\}_{\nu\in\mathbb{N}}$ with respect to $n\times (n-k+1)$ isometries $M_{\nu}$.
Aretaki, Aikaterini, Maroulas, John
core +1 more source
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
semanticscholar +1 more source
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
doaj +1 more source
On the numerical radii of $2\times2$ complex matrices [PDF]
arXiv, 2014 The numerical radius of the general $2\times2$ complex matrix is calculated.
arxiv
A New Class of Operator Monotone Functions via Operator Means
, 2016 In this paper, we obtain a new class of functions, which is developed via the Hermite--Hadamard inequality for convex functions. The well-known one-one correspondence between the class of operator monotone functions and operator connections declares that
Aujla, J. S. +3 more
core +1 more source
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
semanticscholar +1 more source
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
doaj +1 more source
Davis-Wielandt shells of semi-Hilbertian space operators and its applications [PDF]
arXiv, 2019 In this paper we generalize the concept of Davis-Wielandt shell of operators on a Hilbert space when a semi-inner product induced by a positive operator $A$ is considered. Moreover, we investigate the parallelism of $A$-bounded operators with respect to the seminorm and the numerical radius induced by $A$.
arxiv
Pinchings and Positive linear maps
, 2015 We employ the pinching theorem, ensuring that some operators A admit any sequence of contractions as an operator diagonal of A, to deduce/improve two recent theorems of Kennedy-Skoufranis and Loreaux-Weiss for conditional expectations onto a masa in the ...
Bourin, Jean-Christophe, Lee, Eun-Young
core +1 more source
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
semanticscholar +1 more source