Results 41 to 50 of about 513 (80)

ON THE MAXIMAL NUMERICAL RANGE OF ELEMENTARY OPERATORS

, 2017
The notion of the numerical range has been generalized in different directions. One such direction, is the maximal numerical range introduced by Stampfli (1970) to derive an identity for the norm of a derivation on L(H). Unlike the other generalizations,
Mati Runji, John Ogonji Agure, F. Nyamwala   +2 more
semanticscholar   +1 more source

Decomposing numerical ranges along with spectral sets

, 2009
This note is to indicate the new sphere of applicability of the method developed by Mlak as well as by the author.
Szafraniec, F. H.
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

The k-rank numerical radii

, 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

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

On Berezin norm and Berezin number inequalities for sum of operators

Demonstratio Mathematica
The 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, Feki Kais, Minculete Nicusor   +2 more
doaj   +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

Product of operators and numerical range preserving maps

, 2006
Let V be the C∗-algebra B(H) of bounded linear operators acting on the Hilbert space H, or the Jordan algebra S(H) of self-adjoint operators in B(H). For a fixed sequence (i1, . . . , im) with i1, . . . , im ∈ {1, . . . , k}, define a product of A1, . . .
Chi-Kwong Li, Nung-Sing Sze
semanticscholar   +1 more source

Inequalities for the Norm and Numerical Radius of Composite Operators in Hilbert Spaces [PDF]

, 2005
Some new inequalities for the norm and the numerical radius of composite operators generated by a pair of operators are given.Comment: 12 ...
Dragomir, Sever Silvestru
core   +2 more sources

A Survey on Solvable Sesquilinear Forms

, 2017
The aim of this paper is to present a unified theory of many Kato type representation theorems in terms of solvable forms on Hilbert spaces. In particular, for some sesquilinear forms $\Omega$ on a dense domain $\mathcal{D}$ one looks for an expression $$
Corso, Rosario
core   +1 more source