scholarly journals Stability of essential spectra of closed operators under T-compact equivalence and applications

2019 ◽  
Vol 61(12) (1) ◽  
pp. 53-64
Author(s):  
Nassima Khaldi ◽  
◽  
Bekkai Messirdi ◽  
Keyword(s):  
Essential Spectra ◽  
Closed Operators

Unbounded Linear Operators

2018 ◽  
Author(s):  
D. E. Edmunds ◽  
W. D. Evans
Keyword(s):  
Hilbert Spaces ◽  
Linear Operators ◽  
Von Neumann ◽  
Limit Circle ◽  
Sectorial Operators ◽  
Closed Operators ◽  
The Stability ◽  
Symmetric Operators ◽  
Unbounded Linear Operators ◽  
Special Case

This chapter is concerned with closable and closed operators in Hilbert spaces, especially with the special classes of symmetric, J-symmetric, accretive and sectorial operators. The Stone–von Neumann theory of extensions of symmetric operators is treated as a special case of results for compatible adjoint pairs of closed operators. Also discussed in detail is the stability of closedness and self-adjointness under perturbations. The abstract results are applied to operators defined by second-order differential expressions, and Sims’ generalization of the Weyl limit-point, limit-circle characterization for symmetric expressions to J-symmetric expressions is proved.

Closed operators in semi-Hilbertian spaces

2021 ◽  
pp. 1-12
Author(s):  
Hamadi Baklouti ◽  
Sirine Namouri
Keyword(s):  
Closed Operators

scholarly journals Generalized Polar Decompositions for Closed Operators in Hilbert Spaces and Some Applications

2009 ◽  
Vol 64 (1) ◽  
pp. 83-113 ◽  
Author(s):  
Fritz Gesztesy ◽  
Mark Malamud ◽  
Marius Mitrea ◽  
Serguei Naboko
Keyword(s):  
Hilbert Spaces ◽  
Closed Operators

scholarly journals On the n-parameter abstract Cauchy problem

2004 ◽  
Vol 69 (3) ◽  
pp. 383-394
Author(s):  
M. Janfada ◽  
A. Niknam
Keyword(s):  
Banach Space ◽  
Cauchy Problem ◽  
Unique Solution ◽  
Initial Value Problems ◽  
Abstract Cauchy Problem ◽  
Linear Operators ◽  
Uniqueness Of Solution ◽  
Initial Value ◽  
Bounded Linear ◽  
Closed Operators

Let Hi(i = 1, 2, …, n), be closed operators in a Banach space X. The generalised initialvalue problem of the abstract Cauchy problem is studied. We show that the uniqueness of solution u: [0, T1] × [0, T2] × … × [0, Tn] → X of this n-abstract Cauchy problem is closely related to C0-n-parameter semigroups of bounded linear operators on X. Also as another application of C0-n-parameter semigroups, we prove that many n-parameter initial value problems cannot have a unique solution for some initial values.

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