Results 21 to 30 of about 446 (70)
Proper contractions and invariant subspaces
International Journal of Mathematics and Mathematical Sciences, Volume 28, Issue 4, Page 223-230, 2001., 2001 Let T be a contraction and A the strong limit of {T∗nTn}n ≥ 1. We prove the following theorem: if a hyponormal contraction T does not have a nontrivial invariant subspace, then T is either a proper contraction of class 𝒞00 or a nonstrict proper contraction of class 𝒞10 for which A is a completely nonprojective nonstrict proper contraction.
C. S. Kubrusly, N. Levan
wiley +1 more source
Product and factorization of hypo-EP operators
Special Matrices, 2018 In this article, we derive some necessary and sufficient conditions for the product of hypo-EP operators to be hypo-EP and we characterize hypo-EP operators through factorizations.
Johnson P. Sam, Vinoth A.
doaj +1 more source
Fuglede-Putnam theorem and quasisimilarity of class p-wA(s,t) operators
Operators and Matrices, 2019 We show that p -wA(s,t) operators S,T ∗ (s + t 1 , 0 < p 1) with ker(S) ⊆ ker(S∗) and ker(T ∗) ⊆ ker(T ) satisfy Fuglede-Putnam theorem, i.e., SX = XT for some X implies S∗X = XT ∗ .
M. Chō +4 more
semanticscholar +1 more source
Some remarks on the invariant subspace problem for hyponormal operators
International Journal of Mathematics and Mathematical Sciences, Volume 28, Issue 6, Page 359-365, 2001., 2001 We make some remarks concerning the invariant subspace problem for hyponormal operators. In particular, we bring together various hypotheses that must hold for a hyponormal operator without nontrivial invariant subspaces, and we discuss the existence of such operators.
Vasile Lauric
wiley +1 more source
Moore-Penrose inverse of conditional type operators
, 2017 We prove some basic results on some Moore-Penrose inverse of conditional type operators on L2(Σ) . For instance, we show, among other results, that a weighted conditional operator T = MwEMu is centered if and only if T † , the Moore-Penrose inverse of T ,
M. Jabbarzadeh, M. Chegeni
semanticscholar +1 more source
On the projection constants of some topological spaces and some applications
Abstract and Applied Analysis, Volume 6, Issue 5, Page 299-308, 2001., 2001 We find a lower estimation for the projection constant of the projective tensor product X⊗ ∧Y and the injective tensor product X⊗ ∨Y, we apply this estimation on some previous results, and we also introduce a new concept of the projection constants of operators rather than that defined for Banach spaces.
Entisarat El-Shobaky +2 more
wiley +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
Some results on dominant operators
International Journal of Mathematics and Mathematical Sciences, Volume 21, Issue 2, Page 217-220, 1998., 1997 We show that the Weyl spectrum of a dominant operator satisfies the spectral mapping theorem for analytic functions and then answer a question of Oberai.
Youngoh Yang
wiley +1 more source
Factorization of k‐quasihyponormal operators
International Journal of Mathematics and Mathematical Sciences, Volume 14, Issue 3, Page 439-442, 1991., 1989 Let A be the class of all operators T on a Hilbert space H such that R(T*kT), the range space of T*KT, is contained in R(T*k+1), for a positive integer k. It has been shown that if T ϵ A, there exists a unique operator CT on H such that The main objective of this paper is to characterize k‐quasihyponormal; normal, and self‐adjoint operators T in A in ...
S. C. Arora, J. K. Thukral
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On the class of (A,n) - real power positive operators in semi-hilbertian space
Global Journal of Pure and Applied Sciences, 2019 In this paper, the concept of the class of n-Real power positive operators on a hilbert space defined by Abdelkader Benali in [1] is generalized when an additional semi-inner product is considered.
A. Benali
semanticscholar +1 more source