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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…

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

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 give an expression for a generalized numerical radius of Hilbert space operators and then apply it to obtain upper and lower bounds for the generalized numerical radius. We also establish some generalized numerical radius inequalities…

Functional Analysis · Mathematics 2019-09-26 A. Zamani , M. S. Moslehian , Q. Xu , C. Fu

We present new bounds for the numerical radius of bounded linear operators and $2\times 2$ operator matrices. We apply upper bounds for the numerical radius to the Frobenius companion matrix of a complex monic polynomial to obtain new…

Functional Analysis · Mathematics 2020-01-28 Pintu Bhunia , Santanu Bag , Raj Kumar Nayak , Kallol Paul

We obtain upper bounds for the numerical radius of a product of Hilbert space operators which improve on the existing upper bounds. We generalize the numerical radius inequalities of $n\times n$ operator matrices by using non-negative…

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

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

Some elementary inequalities providing upper bounds for the difference of the norm and the numerical radius of a bounded linear operator on Hilbert spaces under appropriate conditions are given.

Functional Analysis · Mathematics 2007-05-23 Sever Silvestru 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…

Functional Analysis · Mathematics 2024-08-23 Pintu Bhunia , Santanu Bag , Kallol Paul

We introduce a new norm on the space of bounded linear operators on a complex Hilbert space, which generalizes the numerical radius norm, the usual operator norm and the modified Davis-Wielandt radius. We study basic properties of this…

Functional Analysis · Mathematics 2024-08-14 D. Sain , P. Bhunia , A. Bhanja , K. Paul

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 article introduces several new upper bounds for the $q$-numerical radius of bounded linear operators on complex Hilbert spaces. Our results refine some of the existing upper bounds in this field. The $q$-numerical radius inequalities…

Functional Analysis · Mathematics 2023-06-08 Arnab Patra , Falguni Roy

In this paper, we present several new bounds for the norm and numerical radius of sums of Hilbert space operators. The obtained bounds form a new collection that enriches our understanding of these bounds. We compare our bounds with the…

Functional Analysis · Mathematics 2026-02-17 Zameddin I. Ismailov , Pembe Ipek Al , 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

We completely characterize Birkhoff-James orthogonality with respect to numerical radius norm in the space of bounded linear operators on a complex Hilbert space. As applications of the results obtained, we estimate lower bounds of…

Functional Analysis · Mathematics 2024-08-13 Arpita Mal , Kallol Paul , Jeet Sen

This paper is a continuation of a recent work on a new norm, christened the $ (\alpha, \beta)$-norm, on the space of bounded linear operators on a Hilbert space. We obtain some upper bounds for the said norm of $n\times n$ operator…

Functional Analysis · Mathematics 2024-08-14 P. Bhunia , A. Bhanja , D. Sain , K. Paul

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 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

In this article, we proved upper bounds for numerical radius of bounded linear operator and product of operators which generalize and improve existing inequalities. We also obtain a numerical radius inequality of invertible operator using…

Functional Analysis · Mathematics 2023-04-03 Raj Kumar Nayak

In this article, we obtain several new weighted bounds for the numerical radius of a Hilbert space operator. The significance of the obtained results is the way they generalize many existing results in the literature; where certain values…

Functional Analysis · Mathematics 2021-03-09 Shiva Sheybani , Mohammed Sababheh , Hamid Reza Moradi
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