Results 31 to 40 of about 435 (74)
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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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
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
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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
wiley +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
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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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Cohyponormal operators with the single valued extension property
International Journal of Mathematics and Mathematical Sciences, Volume 9, Issue 4, Page 659-663, 1986., 1986 It is proved that in order to find a nontrivial hyperinvariant subspace for a cohyponormal operator it suffices to make the further assumption that the operator have the single‐valued extension property.
Ridgley Lange, Shengwang Wang
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Absolute continuity and hyponormal operators
International Journal of Mathematics and Mathematical Sciences, Volume 4, Issue 2, Page 321-335, 1981., 1981 Let T be a completely hyponormal operator, with the rectangular representation T = A + iB, on a separable Hilbert space. If 0 is not an eigenvalue of T* then T also has a polar factorization T = UP, with U unitary. It is known that A, B and U are all absolutely continuous operators.
C. R. Putnam
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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
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Moments from their very truncations
, 2007 It is known that positive definiteness is not enough for the multidimensional moment problem to be solved. We would like throw in to the garden of existing in this matter so far results one more, a result which takes into considerations the utmost ...
Szafraniec, F. H.
core +1 more source