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Let $\mathbb{B}(\mathcal{H})$ be the algebra of all bounded linear operators on a Hilbert space $\mathcal{H}$ and let $N(\cdot)$ be a norm on $\mathbb{B}(\mathcal{H})$. For every $0\leq \nu \leq 1$, we introduce the $w_{_{(N,\nu)}}(A)$ as…

泛函分析 · 数学 2021-11-30 Ali Zamani

In this study, the classical results on the joint numerical radius for $n$-tuples of Hilbert space operators are extended to the setting of the joint $(f,\delta)$-numerical radius. New and diverse contributions to this area are provided,…

泛函分析 · 数学 2026-03-20 Zameddin I. Ismailov , Sergei Silvestrov , Pembe Ipek Al

We establish new upper bounds for the numerical radius of bounded linear operators on a complex Hilbert space by introducing weighted geometric means of the modulus of an operator and its adjoint. This approach yields a family of…

泛函分析 · 数学 2026-02-05 Shankhadeep Mondal , Ram Narayan Mohapatra , Kasun Tharuka Dewage

In this article, we prove an inner product inequality for Hilbert space operators. This inequality, then, is utilized to present a general numerical radius inequality using convex functions. Applications of the new results include obtaining…

泛函分析 · 数学 2022-07-19 Zahra Heydarbeygi , Mohammad Sababheh , Hamid Reza Moradi

We obtain new lower and upper bounds for the numerical radius of a bounded linear operator $A$ on a complex Hilbert space, which refine the existing ones. In particular, if $w(A)$ and $\|A\|$ denote the numerical radius and operator norm of…

泛函分析 · 数学 2026-03-05 Pintu Bhunia , Rukaya Majeed

We prove several singular value inequalities for sum and product of compact operators in Hilbert space. Some of our results generalize the previous inequalities for operators. Also, applications of some inequalities are given.

泛函分析 · 数学 2015-10-02 A. Taghavi , V. Darvish , H. M. Nazari , S. S. Dragomir

We obtain bounds for the numerical radius of $2 \times 2$ operator matrices which improve on the existing bounds. We also show that the inequalities obtained here generalize the existing ones. As an application of the results obtained here…

泛函分析 · 数学 2024-08-23 Pintu Bhunia , Santanu Bag , Kallol Paul

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…

泛函分析 · 数学 2024-04-08 Amit Maji , Atanu Manna , Ram Mohapatra

We present upper and lower bounds for the numerical radius of $2 \times 2$ operator matrices which improves on the existing bound for the same. As an application of the results obtained we give a better estimation for the zeros of a…

泛函分析 · 数学 2024-08-13 Pintu Bhunia , Santanu Bag , Kallol Paul

Let ($\mathcal{H}, \langle . , .\rangle )$ be a complex Hilbert space and $A$ be a positive bounded linear operator on it. Let $w_A(T)$ be the $A$-numerical radius and $\|T\|_A$ be the $A$-operator seminorm of an operator $T$ acting on the…

泛函分析 · 数学 2020-04-17 Nirmal Chandra Rout , Satyajit Sahoo , Debasisha Mishra

New inequalities for the $A$-numerical radius of the products and sums of operators acting on a semi-Hilbert space, i.e. a space generated by a positive semidefinite operator $A$, are established. In particular, it is proved for operators…

泛函分析 · 数学 2020-12-23 Pintu Bhunia , Kais Feki , Kallol Paul

Let $A=\begin{bmatrix} A_{ij} \end{bmatrix}$ be an $n\times n$ operator matrix, where each $A_{ij}$ is a bounded linear operator on a complex Hilbert space. Among other numerical radius bounds, we show that $w(A)\leq w(\hat{A})$, where…

泛函分析 · 数学 2023-03-21 Pintu Bhunia

We obtain several sharp lower and upper bounds for the Euclidean operator radius of a pair of bounded linear operators defined on a complex Hilbert space. As applications of these bounds we deduce a chain of new bounds for the classical…

泛函分析 · 数学 2024-08-14 Suvendu Jana , Pintu Bhunia , Kallol Paul

Several upper and lower bounds for the numerical radius of $2 \times 2$ operator matrices are developed which refine and generalize the earlier related bounds. In particular, we show that if $B,C$ are bounded linear operators on a complex…

泛函分析 · 数学 2024-08-14 Pintu Bhunia , Kallol Paul

The Euclidean operator radius of two bounded linear operators in the Hilbert $C^*$-module over $\A$ is given some precise bounds. Their relationship to recent findings in the literature that offer precise upper and lower bounds on the…

泛函分析 · 数学 2023-07-06 M. H. M. Rashid

In this paper, we introduce a new type of parallelism for bounded linear operators on a Hilbert space $\big(\mathscr{H}, \langle \cdot ,\cdot \rangle\big)$ based on numerical radius. More precisely, we consider operators $T$ and $S$ which…

泛函分析 · 数学 2018-10-25 Marzieh Mehrazin , Maryam Amyari , Ali Zamani

We give an alternative lower bound for the numerical radii of Hilbert space operators. As a by-product, we find conditions such that \begin{equation*} \omega\left(\left[\begin{array}{cc} 0 & R \\ S & 0 \end{array}\right]\right)=\frac{\Vert…

泛函分析 · 数学 2019-03-28 M. Shah Hosseini , B. Moosavi , H. R. Moradi

In this article, we present some new inequalities for numerical radius of Hilbert space operators via convex functions. Our results generalize and improve earlier results by El-Haddad and Kittaneh. Among several results, we show that if…

泛函分析 · 数学 2019-07-16 S. Tafazoli , H. R. Moradi , S. Furuichi , P. Harikrishnan

We prove several numerical radius inequalities for linear operators in Hilbert spaces. It is shown, among other inequalities, that if $A$ is a bounded linear operator on a complex Hilbert space, then \[\omega \left( A \right)\le…

泛函分析 · 数学 2021-06-15 Farzaneh Pouladi Najafabadi , Hamid Reza Moradi

We give new inequalities for $A$-operator seminorm and $A$-numerical radius of semi-Hilbertian space operators and show that the inequalities obtained here generalize and improve on the existing ones. Considering a complex Hilbert space…

泛函分析 · 数学 2024-08-14 Pintu Bhunia , Kallol Paul , Raj Kumar Nayak