Abstract
Diagana (Handbook on operator theory. Springer, Basel, pp 875–880, 2015) studied some sufficient conditions such that if S, T and K are three unbounded linear operators with S being a closed operator, then their algebraic sum \(S+T+K\) is also a closed operator. The main focus of this paper is to extend these results to the closable operator by adding a new concept of the gap and the \(\gamma \)-relative boundedness inspired by the work of Jeribi et al. (Linear Multilinear Algebra 64:1654–1668, 2015). After that, we apply the obtained results to study the specific properties of some block operator matrices.
Similar content being viewed by others
References
Abdelmoumen, B., Jeribi, A., Mnif, M.: Measure of weak noncompactness, some new properties in Fredholm theory, characterization of the Schechter essential spectrum and application to transport operators. Ricerche mat. 61(2), 321–340 (2012)
Banas, J., Goebel, K.: Measures of Noncompactness in Banach Spaces, Pure Appl. Math., Vol. 60. Marcel Dekker: New York (1980)
Diagana, T.: Perturbations of Unbounded Fredholm Linear Operators in Banach spaces. In: Handbouk on Operator Theory, pp. 875–880, Springer, Basel (2015)
Jeribi, A.: Linear Operators and Their Essential Pseudospectra. CRC Press, Boca Raton (2018)
Jeribi, A.: Spectral Theory and Applicatons of Linear Operators and Block Operators Matrices. Springer, New-York (2015)
Jeribi, A., Krichen, B., Zarai Dhahri, M.: Essential spectra of some matrix operators involving \(\gamma \)-relatively bounded entries and an application. Linear Multilinear Algebra 64, 1654–1668 (2015)
Kato, T.: Perturbation theory for linear operator. Classics in Mathematics. Springer, Berlin, 1995. Reprint of the edition (1980)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Ammar, A., Bouzayeni, F. & Jeribi, A. Perturbation of unbounded linear operators by \(\gamma \)-relative boundedness. Ricerche mat 67, 433–445 (2018). https://doi.org/10.1007/s11587-017-0341-0
Received:
Revised:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11587-017-0341-0