Results 51 to 60 of about 513 (80)
Crouzeix's conjecture, compressions of shifts, and classes of nilpotent matrices
Concrete OperatorsThis 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 +4 more
doaj +1 more source
Generalized finite operators and orthogonality
SUT Journal of Mathematics, 2011 In this paper we prove that a spectraloid operator is finite, we present some generalized finite operators and we give a new class of finite op- erators. Also, the orthogonality of some operators is studied.
S. Bouzenada
semanticscholar +1 more source
Bounds of numerical radius of bounded linear operator using $t$-Aluthge transform
, 2020 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.
bag, Santanu +2 more
core
Matrices with defect index one
, 2013 In this paper, we give some characterizations of matrices which have defect index one. Recall that an n -by-n matrix A is said to be of class Sn (resp., S −1 n ) if its eigenvalues are all in the open unit disc (resp., in the complement of closed unit ...
Cheng Chang +4 more
semanticscholar +1 more source
, 2010 Mathematical Subject Classifications (2000): 47A10, 47A56 ...
J. Swoboda, H. K. Wimmer
semanticscholar +1 more source
Characterization of the norm triangle equality in pre-Hilbert C✻-modules and applications
, 2009 The characterization of the norm triangle equality in pre-Hilbert C∗ -modules is given. The result is applied for describing the case of equality in some generalizations of the DunklWilliams inequality.
R. Rajić
semanticscholar +1 more source
Some inequalities for $(\alpha, \beta)$-normal operators in Hilbert spaces
, 2008 An operator $T$ acting on a Hilbert space is called $(\alpha ,\beta)$-normal ($0\leq \alpha \leq 1\leq \beta $) if \begin{equation*} \alpha ^{2}T^{\ast }T\leq TT^{\ast}\leq \beta ^{2}T^{\ast}T.
Dragomir, Sever S. +1 more
core
Higher-rank numerical range in infinite-dimensional Hilbert space
, 2008 In this paper we calculate the higher-rank numerical range, as defined by Choi, Kribs and . Zyczkowski, of selfadjoint operators and of nonunitary isometries on infinite-dimensional Hilbert space.
R. Martínez-Avendaño
semanticscholar +1 more source
, 2002 There exist operators $A$ such that : for any sequence of contractions $\{A_n\}$, there is a total sequence of mutually orthogonal projections $\{E_n\}$ such that $\Sigma E_nAE_n=\bigoplus A_n$.Comment: 11 ...
Bourin, Jean-Christophe
core +1 more source
Normalized numerical ranges of some operators
, 2009 We describe the normalized numerical ranges of certain operators. First, the case of a normal operator, acting in a two dimensional space is considered in detail, leading to the general Kantorovich inequality.
L. Gevorgyan
semanticscholar +1 more source