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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 $A$ be a positive (semidefinite) operator on a complex Hilbert space $\mathcal{H}$ and let $\mathbb{A}=\left(\begin{array}{cc} A & O O & A \end{array}\right).$ We obtain upper and lower bounds for the $A$-Davis-Wielandt radius of…

Functional Analysis · Mathematics 2020-06-11 Aniket Bhanja , Pintu Bhunia , Kallol Paul

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

By the help of power series f we can naturally construct another power series that has as coefficients the absolute values of the coefficients of f. Utilising these functions we prove some inequalities for the spectral radius of the bounded…

Functional Analysis · Mathematics 2013-02-13 S. S. Dragomir

We study the operator symmetric modulus (|Z|+|Z^*|)/2 for matrices Z. Several triangle type inequalities are given.

Functional Analysis · Mathematics 2026-02-24 Jean-Christophe Bourin , Eun-Young Lee

This paper establishes new upper bounds for the $A$-numerical radius of operator matrices in semi-Hilbertian spaces by leveraging the $A$-Buzano inequality and developing refined techniques for operator matrices. We present several sharp…

Functional Analysis · Mathematics 2025-07-08 M. H. M. Rashid

We establish two main inequalities; one for the norm of the second fundamental form and the other for the matrix of the shape operator. The results obtained are for cosymplectic manifolds and, for these, we show that the contact warped…

Differential Geometry · Mathematics 2022-12-16 Abdulqader Mustafa , Ata Assad , Cenap Ozel , Alexander Pigazzini

In this paper, we improve the famous Reid Inequality related to linear operators. Some monotony results for positive operators are also established with a different approach from what is known in the existing literature. Lastly, Reid and…

Functional Analysis · Mathematics 2017-07-12 Souheyb Dehimi , Mohammed Hichem Mortad

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

We introduce and systematically develop two classes of discrete integrable operators: those with $2\times 2$ matrix kernels and those possessing general differential kernels, thereby generalizing the discrete analogue previously studied. A…

Exactly Solvable and Integrable Systems · Physics 2025-11-10 Huan Liu

We study Toeplitz operators with separately radial and radial symbols on the weighted Bergman spaces on the unit ball. The unitary equivalence of such operators with multiplication operators on $\ell^2$ spaces was previously obtained by…

Functional Analysis · Mathematics 2016-01-27 Raul Quiroga-Barranco

In the present paper, we provide several inequalities for the generalized numerical radius of operator matrices as introduced by A. Abu-omar and F. Kittaneh in [3]. We generalize the convexity and the log-convexity results obtained by M.…

Functional Analysis · Mathematics 2020-04-22 H. Abbas , S. Harb , H. Issa

New inequalities for the numerical radius of bounded linear operators defined on a complex Hilbert space $\mathcal{H}$ are given. In particular, it is established that if $T$ is a bounded linear operator on a Hilbert space $\mathcal{H}$…

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

Let $A$ be a bounded linear operator defined on a complex Hilbert space and let $|A|=(A^*A)^{1/2}$ be the positive square root of $A$. Among other refinements of the well known numerical radius inequality $w^2(A)\leq \frac12 \|A^*A+AA^*\|$,…

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

Relatively recently, K.M.R. Audenaert (2010), R.A. Horn and F. Zhang (2010), Z. Huang (2011), A.R. Schep (2011), A. Peperko (2012), D. Chen and Y. Zhang (2015) have proved inequalities on the spectral radius and the operator norm of…

Functional Analysis · Mathematics 2017-12-18 Roman Drnovšek , Aljoša Peperko

In this article we establish Bohr inequalities for operator valued functions, which can be viewed as the analogues of a couple of interesting results from scalar valued settings. Some results of this paper are motivated by the classical…

Complex Variables · Mathematics 2021-01-12 Bappaditya Bhowmik , Nilanjan Das

In this paper, we achieve new and improved numerical radius inequalities of operators defined on a Hilbert space by using Orlicz function and Hermite-Hadamard inequality. The upper bounds of various inequalities involving numerical radii…

Functional Analysis · Mathematics 2024-04-08 Amit Maji , Atanu Manna , Ram Mohapatra

In this article, we present some new inequalities for the numerical radius of products of Hilbert space operators and the generalized Aluthge transform. In particular, we show some upper bounds for $\omega(ABC+DEF)$ using the celebrated…

Functional Analysis · Mathematics 2022-06-03 Mohammad Sababheh , Cristian Conde , Hamid Reza Moradi

We prove an inequality of Hardy type for functions in Triebel-Lizorkin spaces. The distance involved is being measured to a given Ahlfors d-regular set in R^n, with n-1<d<n. As an application of the Hardy inequality, we consider boundedness…

Classical Analysis and ODEs · Mathematics 2012-09-27 Lizaveta Ihnatsyeva , Antti V. Vähäkangas

This paper explores idempotent and nilpotent operators in bicomplex spaces, focusing on their properties and behavior. We define idempotent and nilpotent matrices in this framework and derive related results. Several theorems are presented…

Representation Theory · Mathematics 2025-09-03 Anjali Anjali , Akhil Prakash , Amita Amita , Neeraj Kumar Tomar