[HTML][HTML] Joint numerical ranges of operators in semi-Hilbertian spaces

H Baklouti, K Feki, OAMS Ahmed - Linear algebra and its applications, 2018 - Elsevier
In this paper we aim to investigate the concept of numerical range and maximal numerical
range relative to a positive operator of a d-tuple of bounded linear operators on a Hilbert …

[HTML][HTML] A-numerical radius inequalities for semi-Hilbertian space operators

A Zamani - Linear Algebra and its Applications, 2019 - Elsevier
Let A be a positive bounded operator on a Hilbert space (H,<⋅,⋅>). The semi-inner product<
x, y> A:=< A x, y>, x, y∈ H induces a semi-norm‖⋅‖ A on H. Let‖ T‖ A and w A (T) …

Some improvements of numerical radius inequalities of operators and operator matrices

P Bhunia, K Paul - Linear and Multilinear Algebra, 2022 - Taylor & Francis
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 …

On inequalities for A-numerical radius of operators

P Bhunia, K Paul, RK Nayak - arXiv preprint arXiv:1908.11182, 2019 - arxiv.org
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 …

Products of m-isometries

T Bermúdez, A Martinon, JA Noda - Linear Algebra and its Applications, 2013 - Elsevier
An operator T on a Banach space X is called an (m, p)-isometry if it satisfies the equality∑
k= 0mmk (-1) mk‖ Tkx‖ p= 0, for all x∈ X. In this paper we prove that if T is an (n, p) …

Refinements of A-numerical radius inequalities and their applications

P Bhunia, RK Nayak, K Paul - Advances in Operator Theory, 2020 - Springer
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 …

[HTML][HTML] On tuples of commuting operators in positive semidefinite inner product spaces

K Feki - Linear algebra and its applications, 2020 - Elsevier
This paper is concerned with the study of certain properties of operator tuples on a complex
Hilbert space H when a semi-inner product induced by a positive operator A on H is …

[HTML][HTML] The Cauchy dual and 2-isometric liftings of concave operators

C Badea, L Suciu - Journal of Mathematical Analysis and Applications, 2019 - Elsevier
We present some 2-isometric lifting and extension results for Hilbert space concave
operators. For a special class of concave operators we study their Cauchy dual operators …

[PDF][PDF] A-numerical radius of A-normal operators in semi-Hilbertian spaces

M Faghih-Ahmadi, F Gorjizadeh - Ital. J. Pure Appl. Math, 2016 - ijpam.uniud.it
73 A-NUMERICAL RADIUS OF A-NORMAL OPERATORS IN SEMI-HILBERTIAN SPACES M.
Faghih-Ahmadi1 F. Gorjizadeh 1. Introduction Throughout Page 1 italian journal of pure and …

[PDF][PDF] On (A, m)-expansive operators

S Jung, Y Kim, E Ko, JE Lee - Studia Math, 2012 - researchgate.net
We give several conditions for (A, m)-expansive operators to have the single-valued
extension property. We also provide some spectral properties of such operators. Moreover …