Chtourou, Ines Krichen, Bilel
Published in
Annals of Functional Analysis

In this paper, our central focus is upon a class of linear operators acting on a Banach space X called relatively pseudo weakly demicompact operators. We clarify and determine the relationships with pseudo upper semi-Fredholm and pseudo Fredholm operators. Moreover, a characterization by means of an axiomatic measure of weak noncompactness of linea...

Groenewald, G. J. ter Horst, S. Jaftha, J. Ran, A. C. M.
Published in
Complex Analysis and Operator Theory

This paper concerns the analysis of an unbounded Toeplitz-like operator generated by a rational matrix function having poles on the unit circle T\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{...

Barraa, Mohamed Benabdi, El Hassan Boumazgour, Mohamed
Published in
Advances in Operator Theory

Let A\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathcal {A}}$$\end{document} be a unital complex Banach algebra and let p,q∈A\documentclass[12pt]{minimal} \usepa...

Fonseca, Eli Shapiro, Jacob Sheta, Ahmed Wang, Angela Yamakawa, Kohtaro
Published in
Mathematical Physics, Analysis and Geometry

We study spinful non-interacting electrons moving in two-dimensional materials which exhibit a spectral gap about the Fermi energy as well as time-reversal invariance. Using Fredholm theory we revisit the (known) bulk topological invariant, define a new one for the edge, and show their equivalence (the bulk-edge correspondence) via homotopy.

Yan, Kai Zeng, Qingping Zhu, Yucan
Published in
Complex Analysis and Operator Theory

Let X be a Banach space and A, B, C, D be bounded linear operators on X. In this paper we show that the Drazin (resp. generalized Drazin) spectrum of AC coincides with the Drazin (resp. generalized Drazin) spectrum of BD under certain assumptions. Moreover, several interesting Banach space properties, such as SVEP and polaroidness, are considered.

Groenewald, G. J. ter Horst, S. Jaftha, J. Ran, A. C. M.
Published in
Integral Equations and Operator Theory

This paper contains a further analysis of the Toeplitz-like operators Tω\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$T_\omega $$\end{document} on Hp\documentclass[12...

Fulsche, Robert
Published in
Integral Equations and Operator Theory

Quantization and spectral properties of Toeplitz operators acting on spaces of pluriharmonic functions over bounded symmetric domains and Cn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt...

Zorboska, Nina
Published in
Concrete Operators

We characterize closed range composition operators on the Dirichlet space for a particular class of composition symbols. The characterization relies on a result about Fredholm Toeplitz operators with BMO1 symbols, and with Berezin transforms of vanishing oscillation.

Álvarez, Teresa Keskes, Sonia Mnif, Maher
Published in
Mediterranean Journal of Mathematics

The Samuel multiplicity and the structure of essentially semi-regular linear relations on a Banach space are considered. First, we give some results concerning Samuel multiplicity for essentially semi-regular linear relations. Second, we study the structure of essentially semi-regular linear relations on an infinite dimensional complex Banach space...

Ferjani, Imen Jeribi, Aref Krichen, Bilel
Published in
Mediterranean Journal of Mathematics

In this paper, we investigate the concept of generalized weakly demicompact operators with respect to weakly closed densely defined linear operators. We give their relationship with Fredholm and upper semi-Fredholm operators. In particular a characterization by means of upper semi-Browder spectrum is given. Moreover, we provide some sufficient cond...