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In this paper, more inequalities between the operator norm and its numerical radius, for the class of normal operators, are established. Some of the obtained results are based on recent reverse results for the Schwarz inequality in Hilbert…

Functional Analysis · Mathematics 2012-10-29 Sever Silvestru Dragomir

Let $A$ be a positive operator on a complex Hilbert space $\mathcal{H}.$ We present inequalities concerning upper and lower bounds for $A$-numerical radius of operators, which improve on and generalize the existing ones, studied recently in…

Functional Analysis · Mathematics 2024-08-13 Pintu Bhunia , Kallol Paul , Raj Kumar Nayak

This paper introduces and investigates the concept of the $q$-numerical range for tuples of bounded linear operators in Hilbert spaces. We establish various inequalities concerning the $q$-numerical radius associated with these operator…

Functional Analysis · Mathematics 2024-10-08 Kais Feki , Arnab Patra , Jyoti Rani , Zakaria Taki

The main aim of this article is to establish several $p$-numerical radius inequalities via the $(f,g)$-Aluthge transform of Hilbert space operators and operator matrices. Furthermore, various classical numerical radius and norm inequalities…

Functional Analysis · Mathematics 2025-04-08 Satyajit Sahoo

We present new upper and lower bounds for the numerical radius of a bounded linear operator defined on a complex Hilbert space, which improve on the existing bounds. Among many other inequalities proved in this article, we show that for a…

Functional Analysis · Mathematics 2024-08-13 Pintu Bhunia , Kallol Paul , Raj kumar Nayak

Consider a complex Hilbert space $\left(\mathcal{H}, \langle \cdot, \cdot \rangle\right)$ equipped with a positive bounded linear operator $A$ on $\mathcal{H}$. This induces a semi-norm $\|\cdot\|_A$ through the semi-inner product $\langle…

Functional Analysis · Mathematics 2025-07-09 M. H. M. Rashid

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…

Functional Analysis · Mathematics 2020-10-27 Hamid Reza Moradi , Mohammad Sababheh

In this work, a pre-Gr\"{u}ss inequality for positive Hilbert space operators is proved. So that, some numerical radius inequalities are proved. On the other hand, based on a non-commutative Binomial formula, a non-commutative upper bound…

Functional Analysis · Mathematics 2018-11-21 Mohammad W. Alomari

In this paper, we begin by showing a new generalization of the celebrated Cauchy-Schwarz inequality for the inner product. Then, this generalization is used to present some bounds for the Euclidean operator radius and the Euclidean operator…

Functional Analysis · Mathematics 2023-10-09 Mohammad Sababheh , Hamid Reza Moradi

We develope new lower bounds for the $A$-numerical radius of semi-Hilbertian space operators, and applying these bounds we obtain upper bounds for the $A$-numerical radius of the commutators of operators. The bounds obtained here improve on…

Functional Analysis · Mathematics 2024-08-14 Pintu Bhunia , Kallol Paul

In this work, some generalizations and refinements inequalities for numerical radius of the product of Hilbert space operators are proved. New inequalities for numerical radius of block matrices of Hilbert space operators are also…

Functional Analysis · Mathematics 2019-03-18 Mohammad W. Alomari

This study presents new upper bounds for the numerical radii of operator matrices, with a focus on $n \times n$ and $2 \times 2$ block matrices acting on Hilbert space direct sums. By employing techniques such as the H\"older-McCarthy…

Functional Analysis · Mathematics 2025-08-05 M. H. M. Rashid

We present sharp lower bounds for the A-numerical radius of semi-Hilbertian space operators. We also present an upper bound. Further we compute new upper bounds for the $B$-numerical radius of $2 \times 2$ operator matrices where $B =…

Functional Analysis · Mathematics 2020-04-22 Pintu Bhunia , Raj Kumar Nayak , Kallol Paul

We develop a number of inequalities to obtain bounds for the numerical radius of a bounded linear operator defined on a complex Hilbert space using the properties of $t$-Aluthge transform. We show that the bounds obtained are sharper than…

Functional Analysis · Mathematics 2024-08-13 Santanu bag , Pintu Bhunia , Kallol Paul

This article is devoted to studying some new numerical radius inequalities for Hilbert space operators. Our analysis enables us to improve an earlier bound of numerical radius due to Kittaneh.

Functional Analysis · Mathematics 2020-09-22 Mahdi Ghasvareh , Mohsen Erfanian Omidvar

The main goal of this paper is to present new bounds for certain inner products in Hilbert spaces, with applications to the numerical radius and the operator norm. The obtained results significantly improve earlier results in this…

Functional Analysis · Mathematics 2026-01-06 Mohammad Sababheh , Hamid Reza Moradi

In this work, an improvement of H\"{o}lder-McCarty inequality is established. Based on that, several refinements of the generalized mixed Schwarz inequality are obtained. Consequently, some new numerical radius inequalities are proved. New…

Functional Analysis · Mathematics 2019-03-06 Mohammad W. Alomari

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…

Functional Analysis · Mathematics 2023-08-21 Suvendu Jana , Pintu Bhunia , Kallol Paul

The weighted numerical radius of a Hilbert space operator has been defined recently. This article explores other properties and uses this newly defined numerical radius to obtain several new interesting inequalities for the weighted…

Functional Analysis · Mathematics 2022-04-19 Cristian Conde , Mohammad Sababheh , Hamid Reza Moradi

In this work, some new upper and lower bounds of the Davis-Wielandt radius are introduced. Generalizations of some presented results are obtained. Some bounds of the Davis-Wielandt radius for $n\times n$ operator matrices are established.…

Functional Analysis · Mathematics 2020-08-04 Mohammad W. Alomari