Temat: selfadjoint - Katalog OPAC zbiorów

Skocz do pozycji: 1.

Tytuł:: Reduction of positive self-adjoint extensions
Autorzy:: Tarcsay, Zsigmond
Sebestyén, Zoltán
Powiązania:: https://bibliotekanauki.pl/articles/29519751.pdf
Data publikacji:: 2024
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: positive selfadjoint contractive extension
nonnegative selfadjoint extension
Friedrichs and Krein-von Neumann extension
Opis:: We revise Krein’s extension theory of semi-bounded Hermitian operators by reducing the problem to finding all positive and contractive extensions of the “resolvent operator” $ (I + T)^{−1} $ of $ T $. Our treatment is somewhat simpler and more natural than Krein’s original method which was based on the Krein transform $ (I−T)(I+T)^{−1} $. Apart from being positive and symmetric, we do not impose any further constraints on the operator $ T $: neither its closedness nor the density of its domain is assumed. Moreover, our arguments remain valid in both real or complex Hilbert spaces.
Źródło:: Opuscula Mathematica; 2024, 44, 3; 425-438
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 2.

Tytuł:: Selfadjoint operator matrices with finite rows
Autorzy:: Janas, Jan
Stochel, Jan
Powiązania:: https://bibliotekanauki.pl/articles/1294802.pdf
Data publikacji:: 1997
Wydawca:: Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:: selfadjoint operator
band matrix
weighted shift
Opis:: A generalization of the Carleman criterion for selfadjointness of Jacobi matrices to the case of symmetric matrices with finite rows is established. In particular, a new proof of the Carleman criterion is found. An extension of Jørgensen's criterion for selfadjointness of symmetric operators with "almost invariant" subspaces is obtained. Some applications to hyponormal weighted shifts are given.
Źródło:: Annales Polonici Mathematici; 1997, 66, 1; 155-172
0066-2216
Pojawia się w:: Annales Polonici Mathematici
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 3.

Tytuł:: Minimal realizations of generalized Nevanlinna functions
Autorzy:: Hassi, S.
Wietsma, H. L.
Powiązania:: https://bibliotekanauki.pl/articles/254719.pdf
Data publikacji:: 2016
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: generalized Nevanlinna functions
selfadjoint (multi-valued) operators
minimal realizations
Opis:: Minimal realizations of generalized Nevanlinna functions that carry the information on their generalized poles of nonpositive type in an explicit form are established. These realizations are based on a modification of the basic canonical factorization of generalized Nevanlinna functions whereby the non-minimality problems in realizations that are based directly on the canonical factorization are circumvented.
Źródło:: Opuscula Mathematica; 2016, 36, 6; 749-768
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 4.

Tytuł:: Functional models for Nevanlinna families
Autorzy:: Behrndt, J.
Hassi, S.
Snoo, H. de
Powiązania:: https://bibliotekanauki.pl/articles/255065.pdf
Data publikacji:: 2008
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: symmetric operator
selfadjoint extension
boundary relation
Weyl family
functional model
reproducing kernel Hilbert space
Opis:: The class of Nevanlinna families consists of R-symmetric holomorphic multivalued functions on C \ R with maximal dissipative (maximal accumulative) values on C+ (C-, respectively) and is a generalization of the class of operator-valued Nevanlinna functions. In this note Nevanlinna families are realized as Weyl families of boundary relations induced by multiplication operators with the independent variable in reproducing kernel Hilbert spaces.
Źródło:: Opuscula Mathematica; 2008, 28, 3; 233-245
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 5.

Tytuł:: Eigenvalue estimates for operators with finitely many negative squares
Autorzy:: Behrndt, J.
Mows, R.
Trunk, C.
Powiązania:: https://bibliotekanauki.pl/articles/255926.pdf
Data publikacji:: 2016
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: selfadjoint operator
Krein space
finitely many negative squares
eigenvalue estimate
indefinite Sturm-Liouville operator
Opis:: Let A and B be selfadjoint operators in a Krein space. Assume that the resolvent difference of A and B is of rank one and that the spectrum of A consists in some interval I ⊂ R of isolated eigenvalues only. In the case that A is an operator with finitely many negative squares we prove sharp estimates on the number of eigenvalues of B in the interval I. The general results are applied to singular indefinite Sturm-Liouville problems.
Źródło:: Opuscula Mathematica; 2016, 36, 6; 717-734
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

Skocz do pozycji: 6.

Tytuł:: Multipoint normal differential operators of first order
Autorzy:: Ismailov, Z. I.
Powiązania:: https://bibliotekanauki.pl/articles/952785.pdf
Data publikacji:: 2009
Wydawca:: Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:: differential operator
formally normal and normal operator
multipoint minimal and maximal operators
extension
selfadjoint
accretive and unitary operators
class of compact operators
spectrum of operators and its discreteness
asymptotics of eigenvalues
direct sum of spaces and operators
Opis:: In this paper we discuss all normal extensions of a minimal operator generated by a linear multipoint differential-operator expression of first order in the Hilbert space of vector-functions on the finite interval in terms of boundary and interior point values. Later on, we investigate the structure of the spectrum, its discreteness and the asymptotic behavior of the eigenvalues at infinity for these extensions.
Źródło:: Opuscula Mathematica; 2009, 29, 4; 399-414
1232-9274
2300-6919
Pojawia się w:: Opuscula Mathematica
Dostawca treści:: Biblioteka Nauki

Artykuł

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