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Local Spectral Multiplicity of Selfadjoint Couplings with General Interface Conditions
We consider selfadjoint operators obtained by pasting a finite number of boundary relations with one-dimensional boundary space. A typical example of...
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The Krein transform and semi-bounded extensions of semi-bounded linear relations
The Krein transform is the real counterpart of the Cayley transform and gives a one-to-one correspondence between the positive relations and...
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Functional Models of Symmetric and Selfadjoint Operators
Let A be a closed simple symmetric operator with equal defect numbers acting in a Hilbert space, and let...
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On the Work by Serguei Naboko on the Similarity to Unitary and Selfadjoint Operators
We review Serguei Naboko’s criteria for similarity of an operator to unitary or selfadjoint one, their relation to his functional model, applications...
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Maximally Аccretive and Nonnegative Extensions of a Nonnegative Linear Relation
In terms of spaces of boundary values, we formulate and prove criteria of maximal θ-accretivity and maximal nonnegativity for the proper extension of...
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Perturbations of real parts of eigenvalues of bounded linear operators in a Hilbert space
Let A be a bounded linear operator in a complex separable Hilbert space ℌ, and S be a selfadjoint operator in ℌ. Assuming that A − S belongs to the...
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On properties of real selfadjoint operators
In spite of the important applications of real selfadjoint operators and monotone operators, very few papers have dealt in depth with the properties...
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Perturbation theory for selfadjoint relations
We study Weyl-type perturbation theorems in the context of closed linear relations. General results on perturbations for dissipative relations are...
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Local Refinement of Solutions in the Finite Element Method
We propose an approach to a posteriori improvement of approximations in projection methods for solving linear equations with selfadjoint positive...
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Dilatations of Linear Operators
The article is devoted to building various dilatations of linear operators. The explicit construction of a unitary dilation of a compression operator...
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The Space of Bounded Operators on a Hilbert Space as Ordered Vector Space
This chapter is a study of the space of bounded operators on any complex Hilbert space as a pedagogical model of C∗-algebra. We explain in particular...
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Singular perturbations of unbounded selfadjoint operators Reverse approach
Let A and A1 be unbounded selfadjoint operators in a Hilbert space $$ \mathcal...