Results 31 to 40 of about 469 (43)
Closable Hankel operators and moment problems
, 2019 In a paper from 2016 D. R. Yafaev considers Hankel operators associated with Hamburger moment sequences q_n and claims that the corresponding Hankel form is closable if and only if the moment sequence tends to 0.
Berg, Christian, Szwarc, Ryszard
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On the triviality of domains of powers and adjoints of closed operators
, 2018 The paper is devoted to counterexamples involving the triviality of domains of products and/or adjoints of densely defined ...
Mortad, Mohammed Hichem
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Elliptic operators and their symbols
Demonstratio Mathematica, 2019 We consider special elliptic operators in functional spaces on manifolds with a boundary which has some singular points. Such an operator can be represented by a sum of operators, and for a Fredholm property of an initial operator one needs a Fredholm ...
Vasilyev Vladimir
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Unbounded Hankel operators and moment problems
, 2019 We find simple conditions for a non-negative Hankel quadratic form to be closable. Under some mild a priori assumption on the associated moments these sufficient conditions turn out to be also necessary.
Yafaev, D. R.
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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.
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On semibounded Toeplitz operators
, 2016 We show that a semibounded Toeplitz quadratic form is closable in the space $\ell^2({\Bbb Z}_{+})$ if and only if its matrix elemens are Fourier coefficients of an absolutely continuous measure.
Yafaev, D. R.
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A distance formula related to a family of projections orthogonal to their symmetries
, 2017 Let u be a hermitian involution, and e an orthogonal projection, acting on the same Hilbert space. We establish the exact formula, in terms of the norm of eue, for the distance from e to the set of all orthogonal projections q from the algebra generated ...
Spitkovsky, Ilya M.
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A new extended Mulholland's inequality involving one partial sum
Open MathematicsBy using the weight coefficients and the techniques of real analysis, a new extended Mulholland’s inequality with multi-parameters involving one partial sum is given. The equivalent statements of the best value related to several parameters are provided.
Peng Ling, Yang Bicheng
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Demonstratio MathematicaIf T1{{\mathbb{T}}}_{1} and T2{{\mathbb{T}}}_{2} are commuting dd-tuples of Hilbert space operators in B(ℋ)dB{\left({\mathcal{ {\mathcal H} }})}^{d} such that (T1*⊗I+I⊗T2*,T1⊗I+I⊗T2)\left({{\mathbb{T}}}_{1}^{* }\otimes I+I\otimes {{\mathbb{T}}}_{2}^{* },{
Duggal Bhagwati Prashad, Kim In Hyoun
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What is a proper graph Laplacian? An operator-theoretic framework for graph diffusion
Special MatricesWe introduce an operator-theoretic definition of a proper graph Laplacian as any matrix associated with a given graph that can be expressed as the composition of a divergence and a gradient operator, with the gradient acting between graph-related spaces ...
Estrada Ernesto
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