Results 31 to 40 of about 82 (79)

Crouzeix's conjecture, compressions of shifts, and classes of nilpotent matrices

Concrete Operators
This article studies the level set Crouzeix (LSC) conjecture, which is a weak version of Crouzeix’s conjecture that applies to finite compressions of the shift.
Bickel Kelly, Corbett Georgia, Glenning Annie, Guan Changkun, Vollmayr-Lee Martin   +4 more
doaj   +1 more source

On the spectral norm of a doubly stochastic matrix and level-k circulant matrix

Special Matrices
A simple proof using Birkhoff theorem is given for the result that the spectral norm of a doubly stochastic matrix is 1. We also show that the result generalizes the results of İpek, Bozkurt, and Jiang and Zhou on circulant matrices and rr-circulant ...
Jiang Zhao-Lin, Tam Tin-Yau
doaj   +1 more source

Enhanced Young-type inequalities utilizing Kantorovich approach for semidefinite matrices

Open Mathematics
This article introduces new Young-type inequalities, leveraging the Kantorovich constant, by refining the original inequality. In addition, we present a range of norm-based inequalities applicable to positive semidefinite matrices, such as the Hilbert ...
Bani-Ahmad Feras, Rashid Mohammad Hussein Mohammad   +1 more
doaj   +1 more source

Isometries Between Matrix Algebras

, 2007
As an attempt to understand linear isometries between C # -algebras without the surjectivity assumption, we study linear isometries between matrix algebras. Denote by Mm the algebra of mm complex matrices. If k n and # : M n k has the form
Chi-kwong Li, Yiu-tung Poon, Wai-shun Cheung, Wai-Shun Cheung Chi-Kwong   +3 more
core  

Interpolation $H^{\infty}$ et théorèmes de plongements pour des fonctions rationnelles

, 2019
International audienceWe consider a Nevanlinna-Pick interpolation problem on finite sequences of the unit disc D constrained by Hardy and radial-weighted Bergman norms. We find sharp asymptotics on the corresponding interpolation constants.
Baranov, Anton, Zarouf, Rachid
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If A Matrix Has Only A Single Eigenvalue How Sensitive Is This Eigenvalue?

, 1997
. For matrices with a single eigenvalue we analyse the sensitivity of the eigenvalue to perturbations in the matrix. We derive a closed form result that is similar in spirit to an analytical result by Lidskii; improve a bound by Henrici; and express the ...
Grace E. Cho, Ilse C.F. Ipsen
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Fejér–Riesz factorization in the QRC-subalgebra and circularity of the quaternionic numerical range

Journal Article, Faculty of Natural and Agricultural Sciences, Pure and Applied Analytics -- Potchefstroom CampusWe provide a characterization when the quaternionic numerical range of a matrix is a closed ball with center 0.
Van Straaten, Madelein, Vander Merwe, Alma, Woerdeman, Hugo J   +2 more
core   +1 more source

HIGHER-RANK NUMERICAL RANGES AND DILATIONS

, 2008
. For any n-by-n complex matrix A and any k, 1 ≤ k ≤ n, let Λ k(A) = {λ ∈ C: X ∗ AX = λI k for some n-by-k X satisfying X ∗ X = I k} be its rank-k numerical range.
Hwa-long Gau, Chi-kwong Li, Pei Yuan Wu
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The c-numerical range of a quaternion skew-Hermitian matrix is convex

Journal Article, Faculty of Natural and Agricultural Sciences, Pure and Applied Analytics-- Potchefstroom CampusWe show that the c-numerical range of a non-scalar skew-Hermitian quaternion matrix is convex.
Thiersen, Madelein, Vander Merwe, Alma, Woerdeman, Hugo J   +2 more
core   +1 more source

Relative Perturbation Bound for Invariant Subspaces of Indefinite Hermitian Matrix

, 1998
We give bound for the perturbations of invariant subspaces of nonsingular indefinite Hermitian matrix H under relative additive perturbations of H. Such perturbations include the case when the elements of H are known up to some relative tolerance.
Ivan Slapnicar, Ninoslav Truhar
core