Results 241 to 250 of about 594,472 (279)

ON THE EXTENSIONS AND THE CHARACTERISTIC FUNCTION OF A SYMMETRIC OPERATOR

Mathematics of the USSR-Izvestiya, 1968
In this paper we describe a class of dissipative and accumulative extensions of a symmetric operator A acting in a Hilbert space H. The concept of the characteristic function of an operator A is defined in terms of such extensions, and its boundary values are studied.
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Bounded characteristic functions and models for noncontractive sequences of operators

Integral Equations and Operator Theory, 2003
In the paper under review, the Sz.-Nagy-Foiaş functional model for completely non-unitary contractions is extended to completely non-coisometric sequences of bounded operators on a Hilbert space \(H\). It was shown in [\textit{B. Sz.-Nagy} and \textit{C. Foiaş}, C. R. Acad.
Gheondea, Aurelian, Popescu, Gelu
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Expansions in Characteristic Vectors of Nonunitary Operators and the Characteristic Function

1970
In this paper we shall establish necessary and sufficient conditions for a system of characteristic vectors of a nonunitary operator in Hilbert space to form an unconditional basis (i.e., a basis similar to an orthonormal basis). These conditions will be formulated in terms of the characteristic function of the operator and its functional model, as ...
N. K. Nikol’skii, B. S. Pavlov
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Reference functional and characteristic space for Lagrange and Bernstein operators

Approximation Theory and its Applications, 1995
The authors apply the concept of reference functionals and characteristic spaces, introduced in [\textit{C. Brezinski} and the reviewer, J. Comput. Appl. Math. 34, No. 3, 361-383 (1991; Zbl 0732.65004)], to the case of multivariate polynomials over simplices. In particular, they consider interpolating polynomials, computed by the de Casteljau operator.
DE MARCHI, STEFANO, M. MORANDI CECCHI
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Automorphic-invariant operator colligations and the factorization of their characteristic operator functions

Functional Analysis and Its Applications, 1987
In these notes is given an exposition focused on the automorphically invariant operator nodes and factorization of their characteristic operator-functions.
Filimonov, A. P., Tsekanovskij, Eh. R.
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Unitary Systems and Characteristic Operator Functions

1993
This chapter presents an introduction to the theory of unitary systems and their transfer functions. We already met transfer functions of the form I + C(λ − A)-1 B in earlier chapters. Here we are concerned with the case when the system matrix is a unitary operator acting on an infinite dimensional Hilbert space.
I. Gohberg, M. A. Kaashoek, S. Goldberg
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Regular factorizations of a characteristic function and singular operator-functions

Functional Analysis and Its Applications, 1991
Regular factorizations of contractive characteristic functions are studied in the book of \textit{B. Sz.-Nagy} and \textit{C. Foiaş} [Harmonic analysis of operators on Hilbert space. Budapest: Akadémiai Kiadó (1970; Zbl 0201.45003), Chapter 7]. It is shown that they correspond to invariant subspaces for the associated operator.
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The Krein String and Characteristic Functions of Maximal Dissipative Operators

Journal of Mathematical Sciences, 2004
zbMATH Open Web Interface contents unavailable due to conflicting licenses.
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Characteristic Functions of Maximal Sectorial Operators

2001
The analytic properties of the characteristic functions of maximal sectorial operators are studied and functional models are constructed.
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On characteristic functions of maximal dissipative operators

Complex Analysis and Operator Theory
zbMATH Open Web Interface contents unavailable due to conflicting licenses.
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