Results 21 to 30 of about 2,288,250 (268)

Some Inequalities for the Euclidean Operator Radius of Two Operators in Hilbert Spaces [PDF]

, 2006
Some sharp bounds for the Euclidean operator radius of two bounded linear operators in Hilbert spaces are given. Their connection with Kittaneh’s recent results which provide sharp upper and lower bounds for the numerical radius of linear operators ...
Dragomir, Sever S
core   +7 more sources

New estimates for the numerical radius

Filomat, 2021
In this article, we present new inequalities for the numerical radius of the sum of two Hilbert space operators. These new inequalities will enable us to obtain many generalizations and refinements of some well known inequalities, including multiplicative behavior of the numerical radius and norm bounds. Among many other applications, it is
Moradi, Hamid Reza, Sababheh, Mohammad
openaire   +3 more sources

Gap Between Operator Norm and Spectral Radius for the Square of Antidiagonal Block Operator Matrices

Communications in Advanced Mathematical Sciences, 2022
In this work, the gap between operator norm and spectral radius for the square of antidiagonal block operator matrices in the direct sum of Banach spaces has been investigated, and also the gap between operator norm and numerical radius for the square of
Elif Otkun Çevik
doaj   +1 more source

Some Results on Polynomial Numerical Hulls of Perturbed Matrices [PDF]

Sahand Communications in Mathematical Analysis, 2019
In this paper, the behavior of the pseudopolynomial numerical hull of a square complex matrix with respect to structured perturbations and its radius is investigated.
Madjid Khakshour, Gholamreza Aghamollaei
doaj   +1 more source

On Some Inequalities for the Generalized Euclidean Operator Radius

Axioms, 2023
In the literature, there are many criteria to generalize the concept of a numerical radius; one of the most recent and interesting generalizations is the so-called generalized Euclidean operator radius, which reads: ωpT1,⋯,Tn:=supx=1∑i=1nTix,xp1/p,p≥1 ...
Mohammad W. Alomari, Gabriel Bercu, Christophe Chesneau, Hala Alaqad   +3 more
doaj   +1 more source

Numerical radius orthogonality in $$C^*$$-algebras [PDF]

Annals of Functional Analysis, 2020
In this paper we characterize the Birkhoff--James orthogonality with respect to the numerical radius norm $v(\cdot)$ in $C^*$-algebras. More precisely, for two elements $a, b$ in a $C^*$-algebra $\mathfrak{A}$, we show that $a\perp_{B}^{v} b$ if and only if for each $θ\in [0, 2π)$, there exists a state $φ_{_θ}$ on $\mathfrak{A}$ such that $|φ_{_θ}(a)| =
Zamani, Ali, Wójcik, Paweł
openaire   +2 more sources

Some inequalities for the numerical radius and rhombic numerical radius

Kragujevac Journal of Mathematics, 2018
Summary: In this paper, the definition rhombic numerical radius is introduced and we present several numerical radius inequalities. Some applications of these inequalities are considered as well. Particular, it is shown that, if \(A\in\mathcal{B}(\mathcal{H})\) with the Cartesian decomposition \(A=C+iD\) and \(r\geq 1\), then \[ \begin{aligned}\omega^r(
Bajmaeh, Akram Babri, Omidvar, Mohsen Erfanian   +1 more
openaire   +2 more sources

Refinements of numerical radius inequalities using the Kantorovich ratio

Concrete Operators, 2022
In this paper, we improve some numerical radius inequalities for Hilbert space operators under suitable condition. We also compare our results with some known results. As application of our result, we obtain an operator inequality.
Nikzat Elham, Omidvar Mohsen Erfanian
doaj   +1 more source

Bounding the Zeros of Polynomials Using the Frobenius Companion Matrix Partitioned by the Cartesian Decomposition

Algorithms, 2022
In this work, some new inequalities for the numerical radius of block n-by-n matrices are presented. As an application, the bounding of zeros of polynomials using the Frobenius companion matrix partitioned by the Cartesian decomposition method is proved.
Mohammad W. Alomari, Christophe Chesneau
doaj   +1 more source

NUMERICAL RADIUS NORMS ON OPERATOR SPACES [PDF]

Journal of the London Mathematical Society, 2006
We introduce a numerical radius operator space $(X, \mathcal{W}_n)$. The conditions to be a numerical radius operator space are weaker than the Ruan's axiom for an operator space $(X, \mathcal{O}_n)$. Let $w(\cdot)$ be the numerical radius norm on $\mathbb{B}(\mathcal{H})$.
Itoh, T., Nagisa, M.
openaire   +2 more sources