Results 1 to 10 of about 865 (99)

Reverse Inequalities for the Numerical Radius of Linear Operators in Hilbert Spaces [PDF]

arXiv, 2005
Some elementary inequalities providing upper bounds for the difference of the norm and the numerical radius of a bounded linear operator on Hilbert spaces under appropriate conditions are given.
Dragomir, Sever Silvestru
arxiv   +4 more sources

Decomposing numerical ranges along with spectral sets [PDF]

arXiv, 2009
This note is to indicate the new sphere of applicability of the method developed by Mlak as well as by the author. Restoring those ideas is summoned by current developments concerning $K$-spectral sets on numerical ranges.
Szafraniec, F. H.
arxiv   +3 more sources

Compressions and Pinchings [PDF]

arXiv, 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 $\Sigma E_nAE_n=\bigoplus A_n$.
Bourin, Jean-Christophe
arxiv   +3 more sources

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

arXiv, 2005
Some new inequalities for the norm and the numerical radius of composite operators generated by a pair of operators are given.
Dragomir, Sever Silvestru
arxiv   +4 more sources

Further refinements of some numerical radius inequalities for operators

Operators and Matrices, 2023
. In this work, we give re fi nements of some well-known numerical radius inequalities. Also, we present an improvement of the triangle inequality for the operator norm. Mathematics subject classi fi cation (2020): 47A12, 47A30, 47B15.
Soumia Soltani, Abdelkader Frakis
semanticscholar   +1 more source

Preservers of the c-numerical radius of operator jordan semi-triple products

Operators and Matrices, 2021
Let H be a complex Hilbert space with dimH 3 , let B(H ) be the algebra of all bounded linear operators on H and let Bs(H ) be the real Jordan algebra of all self-adjoint operators in B(H ) . Let A = B(H ) or Bs(H ) .
Y. Zhang, X. Fang
semanticscholar   +1 more source

New class of operators where the distance between the identity operator and the generalized Jordan ∗-derivation range is maximal

Demonstratio Mathematica, 2021
A new class of operators, larger than ∗\ast -finite operators, named generalized ∗\ast -finite operators and noted by Gℱ∗(ℋ){{\mathcal{G {\mathcal F} }}}^{\ast }\left({\mathcal{ {\mathcal H} }}) is introduced, where: Gℱ∗(ℋ)={(A,B)∈ℬ(ℋ)×ℬ(ℋ):∥TA−BT∗−λI ...
Messaoudene Hadia, Mesbah Nadia
doaj   +1 more source

A Chain of numerical radius inequalities in complex Hilbert space

Journal of Mathematical Inequalities, 2021
In this paper, we implement the improvement of numerical radius inequalities that were produced by Alomari MW. [Refinements of some numerical radius inequalities for Hilbert space operators. Linear and Multilinear Algebra.
Mohammed Al-Dolat, Ayat Dagher, Marwan Alquran   +2 more
semanticscholar   +1 more source

Volterra operator norms : a brief survey

Moroccan Journal of Pure and Applied Analysis, 2023
In this expository article, we discuss the evaluation and estimation of the operator norms of various functions of the Volterra operator.
Ransford Thomas
doaj   +1 more source

On partial isometries with circular numerical range

Concrete Operators, 2021
In their LAMA 2016 paper Gau, Wang and Wu conjectured that a partial isometry A acting on ℂn cannot have a circular numerical range with a non-zero center, and proved this conjecture for n ≤ 4. We prove it for operators with rank A = n − 1 and any n.
Wegert Elias, Spitkovsky Ilya
doaj   +1 more source