Results 11 to 20 of about 233 (33)
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 31, Page 1993-2002, 2003., 2003 We introduce the concept of quasireducible operators. Basic properties and illustrative examples are considered in some detail in order to situate the class of quasireducible operators in its due place. In particular, it is shown that every quasinormal operator is quasireducible. The following result links this class with the invariant subspace problem:
C. S. Kubrusly
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On the largest analytic set for cyclic operators
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 30, Page 1899-1909, 2003., 2003 We describe the set of analytic bounded point evaluations for an arbitrary cyclic bounded linear operator T on a Hilbert space ℋ; some related consequences are discussed. Furthermore, we show that two densely similar cyclic Banach‐space operators possessing Bishop′s property (β) have equal approximate point spectra.
A. Bourhim
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Some versions of Anderson′s and Maher′s inequalities I
International Journal of Mathematics and Mathematical Sciences, Volume 2003, Issue 52, Page 3281-3297, 2003., 2003 We prove the orthogonality (in the sense of Birkhoff) of the range and the kernel of an important class of elementary operators with respect to the Schatten p‐class.
Salah Mecheri
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Generalized derivation modulo the ideal of all compact operators
International Journal of Mathematics and Mathematical Sciences, Volume 32, Issue 8, Page 501-506, 2002., 2002 We give some results concerning the orthogonality of the range and the kernel of a generalized derivation modulo the ideal of all compact operators.
Salah Mecheri, Ahmed Bachir
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Strongly exposed points in the unit ball of trace‐class operators
International Journal of Mathematics and Mathematical Sciences, Volume 30, Issue 7, Page 393-397, 2002., 2002 A theorem of Arazy shows that every extreme point of the unit ball of trace‐class operators is strongly exposed. We give this result a simpler and direct proof here.
Kourosh Nourouzi
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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
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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
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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
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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
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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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