Results 71 to 80 of about 81,652 (161)

On the unitary invariance of the numerical radius [PDF]

Pacific Journal of Mathematics, 1978
Filippenko, Ivan, Marcus, Marvin
openaire   +2 more sources

Euclidean operator radius and numerical radius inequalities

Operators and Matrices
Let $T$ be a bounded linear operator on a complex Hilbert space $\mathscr{H}.$ We obtain various lower and upper bounds for the numerical radius of $T$ by developing the Euclidean operator radius bounds of a pair of operators, which are stronger than the existing ones. In particular, we develop an inequality that improves on the inequality $$ w(T) \geq
Jana, Suvendu, Bhunia, Pintu, Paul, Kallol   +2 more
openaire   +2 more sources

On a Numerical Radius Preserving Onto Isometry on L(X)

Journal of Function Spaces, 2016
We study a numerical radius preserving onto isometry on L(X). As a main result, when X is a complex Banach space having both uniform smoothness and uniform convexity, we show that an onto isometry T on L(X) is numerical radius preserving if and only if ...
Sun Kwang Kim
doaj   +1 more source

Strengthening of spectral radius, numerical radius, and Berezin radius inequalities

Revista de la Real Academia de Ciencias Exactas, Físicas y Naturales. Serie A. Matemáticas
Suppose $\mathcal{H}_1, \mathcal{H}_2, \ldots, \mathcal{H}_n$ are arbitrary complex Hilbert spaces, and ${\bf A}=[A_{ij}]$ is an $n\times n$ operator matrix with $A_{ij}\in \mathcal{B}(\mathcal{H}_j, \mathcal{H}_i).$ We show that $w({\bf A}) \leq w\left(\begin{bmatrix} a_{ij} \end{bmatrix}_{i,j=1}^n \right),$ where $w(\cdot)$ denotes the numerical ...
openaire   +2 more sources

The Ratios Between The Spectral Norm, The Numerical Radius And The Spectral Radius

World Academy of Science, Engineering and Technology, 2010
{"references": ["B. Beckermann, S. A. Goreinov, and E. E. Tyrtyshnikov. Some Remarks\non the Elman Estimate for GMRES. SIAM J. Matrix Anal. Appl.,\n27(3):772-778, 2006.", "L. Caston, M. Savova, I. Spitkovsky, and N. Zobin. On eigenvalues\nand boundary curvature of the numerical range. Linear Algebra Appl.,\n322(1-3):129-140, 2001.", "M. Eiermann and O.
openaire   +5 more sources

Numerical radius equalities and inequalities for Hilbert space operators [PDF]

Surveys in Mathematics and its Applications
We give new numerical radius equalities and inequalities for Hilbert space operators. Also, we provide some upper bounds for the numerical radii of certain 2 × 2 operator matrices.
Abdelkader Frakis, Fuad Kittaneh
doaj  

Numerical radius inequalities

, 2022
We introduce some basic theory about numerical range and numerical radius. Basic inequalities for numerical radius which involve one operator and basic inequalities which involve product of two commutative operators are studied. We then introduce more complex numerical radius inequalities for one operator, finding some upper bounds for the nonnegative ...
openaire   +1 more source

Accounting for vertical well imperfection in a two-dimensional reservoir model

Учёные записки Казанского университета: Серия Физико-математические науки
In this study, a methodology is proposed to account for vertical well imperfection, depending on the degree of reservoir penetration, in a two-dimensional vertically averaged numerical flow model of a heterogeneous reservoir.
I. V. Eremin, D. R. Salimyanova, K. A. Potashev   +2 more
doaj   +1 more source

Some numerical radius inequalities for d-tuples of operators [PDF]

Surveys in Mathematics and its Applications
Our aim in this paper is to give new numerical radius inequalities for d-tuples of operators on a complex Hilbert space. We prove several inequalities for multivarible operators on a complex Hilbert space. Based on that some numerical radius inequalities
Messaoud Guesba, Ould Ahmed Mahmoud Sid Ahmed   +1 more
doaj  

Improvements of Some Numerical radius inequalities

, 2019
In this work, we improve and refine some numerical radius inequalities. In particular, for all Hilbert space operators $T$, the celebrated Kittaneh inequality reads: \begin{align*} \frac{1}{4}\left\| T^*T + TT^*\right\|\le w^{2 }\left(T \right) \le \frac{1}{2}\left\| T^*T + TT^*\right\|.
openaire   +3 more sources