Results 41 to 50 of about 865 (99)
Domaine Numérique du produit AB avec A normal [PDF]
, 2006 2000 Mathematics Subject Classification: 18B30, 47A12.Let A, B be two linear operators on a complex Hilbert space H. We extend a Bouldin's result (1969) conserning W(AB) - the numerical range of the product AB. We show, when AB = BA and A is normal, than
Kaadoud, Mohamed Chraïbi
core
Numerical radius inequalities associated with the Cartesian decomposition
, 2015 We give several sharp numerical radius inequalities associated with the Cartesian decomposition of a Hilbert space operator A = B + iC . Among other inequalities, it is shown that 1 2 ‖ |B| + |C|‖ wr(A) ‖ |B| + |C|‖ for 0 < r 2 , where w(·) and ...
F. Kittaneh
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Convexity around the Unit of a Banach Algebra [PDF]
, 2008 2000 Mathematics Subject Classification: Primary: 46B20. Secondary: 46H99, 47A12.We estimate the (midpoint) modulus of convexity at the unit 1 of a Banach algebra A showing that inf {max±||1 ± x|| − 1 : x ∈ A, ||x||=ε} ≥ (π/4e)ε²+o(ε²) as ε → 0. We also
Kadets, Vladimir +3 more
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Scalar approximants of quadratic operators with applications
, 2018 Among other results, we find the best scalar approximant of a quadratic operator with respect to the numerical radius and the operator norm. We use these results to give estimates for the numerical radii of products and commutators of quadratic operators.
A. Abu-Omar, P. Wu
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The joint essential numerical range of operators: convexity and related results
, 2009 LetW (A) andWe(A) be the joint numerical range and the joint essential numerical range of an m-tuple of self-adjoint operators A = (A1, . . . , Am) acting on an infinite dimensional Hilbert space, respectively.
Chi-Kwong Li, Y. Poon
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A fiedler-type theorem for the determinant of J-positive matrices
, 2016 In this note we characterize the set of all possible values attained by the determinant of the sum of two J -positive matrices with prescribed spectra, under a natural compatibility condition. Mathematics subject classification (2010): 46C20, 47A12.
N. Bebiano, J. Providência
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Norms of polynomials of the Volterra operator [PDF]
arXiv, 2022 We compute the operator norm of real-quadratic polynomials of the Volterra operator. This is used to test whether the Crouzeix conjecture holds for the Volterra operator.
arxiv
On the block numerical range of operators on arbitrary Banach spaces
, 2018 We investigate the block numerical range of bounded linear operators on arbitrary Banach spaces. We show that the spectrum of an operator is always contained in the closure of its block numerical range.
Agnes Radl, M. Wolff
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Advancement of numerical radius inequalities of operator and product of operators [PDF]
arXiv, 2023 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 Kantorovich's ratio.
arxiv
ON THE MAXIMAL NUMERICAL RANGE OF ELEMENTARY OPERATORS
, 2017 The notion of the numerical range has been generalized in different directions. One such direction, is the maximal numerical range introduced by Stampfli (1970) to derive an identity for the norm of a derivation on L(H). Unlike the other generalizations,
Mati Runji +2 more
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