Results 31 to 40 of about 865 (99)
Constant norms and numerical radii of matrix powers
Operators and Matrices, 2019 For an n -by-n complex matrix A , we consider conditions on A for which the operator norms ‖Ak‖ (resp., numerical radii w(Ak) ), k 1 , of powers of A are constant.
Hwa-Long Gau, Kuo-Zhong Wang, P. Wu
semanticscholar +1 more source
Sesquilinear version of numerical range and numerical radius
Acta Universitatis Sapientiae: Mathematica, 2017 In this paper by using the notion of sesquilinear form we introduce a new class of numerical range and numerical radius in normed space 𝒱, also its various characterizations are given. We apply our results to get some inequalities.
Moradi Hamid Reza +3 more
doaj +1 more source
An observation about normaloid operators
, 2017 Let H be a complex Hilbert space and B(H) the Banach space of all bounded linear operators on H . For any A ∈ B(H) , let w(A) denote the numerical radius of A . Then A is normaloid if w(A) = ‖A‖ .
J. Chan, K. Chan
semanticscholar +1 more source
Numerical radius attaining compact linear operators [PDF]
J. Math. Anal. Appl. 445 (2017), 1258-1266, 2016 We show that there are compact linear operators on Banach spaces which cannot be approximated by numerical radius attaining operators.
arxiv +1 more source
Remarks on the Crouzeix-Palencia proof that the numerical range is a $(1+\sqrt2)$-spectral set
, 2018 Crouzeix and Palencia recently showed that the numerical range of a Hilbert-space operator is a $(1+\sqrt2)$-spectral set for the operator. One of the principal ingredients of their proof can be formulated as an abstract functional-analysis lemma.
Ransford, Thomas, Schwenninger, Felix
core +1 more source
Generalized Derivations and Norm Equality in Normed Ideals [PDF]
, 2011 2000 Mathematics Subject Classification: 47A10, 47A12, 47A30, 47B10, 47B20, 47B37, 47B47, 47D50.We compare the norm of a generalized derivation on a Hilbert space with the norm of its restrictions to Schatten norm ...
Barraa, Mohamed
core
Sequences of bounds for the spectral radius of a positive operator
, 2019 In 1992, Szyld provided a sequence of lower bounds for the spectral radius of a nonnegative matrix $A$, based on the geometric symmetrization of powers of $A$.
Drnovšek, Roman
core +1 more source
On the normalized numerical range
, 2017 The normalized numerical range of an operator A is defined as the set FN(A) of all the values 〈Ax,x〉/‖Ax‖ attained by unit vectors x / ∈ kerA . We prove that FN(A) is simply connected, establish conditions for it to be star-shaped with the center at zero,
I. Spitkovsky, A. Stoica
semanticscholar +1 more source
Numerical radius inequalities of operator matrices with applications
, 2020 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.
Bag, Santanu +2 more
core +1 more source
Two-dimensional Banach spaces with Polynomial numerical index zero [PDF]
, 2009 We study two-dimensional Banach spaces with polynomial numerical indices equal to zero.
arxiv +1 more source