Über analytische Operatorfunktionen und Indexberechnung
Über das Wachstum von Resolventen in der Nähe einer isolierten Singularität.
Über ein Transmissionsproblem mit Integro-Differentialbedingungen.
Über holomorphe und meromorphe einseitige Inverse.
Un théorème de l'indice relatif
Una caracterización de los operadores de Fredholm y semi-Fredholm.
Unbounded linear transformations of upper semi-Fredholm type in normed spaces
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Upper and Lower Fredholm Spectra II.
Verwandte Operatoren.
Weyl spectra and Weyl's theorem
"Weyl's theorem" for an operator on a Hilbert space is the statement that the complement in the spectrum of the Weyl spectrum coincides with the isolated eigenvalues of finite multiplicity. In this paper we consider how Weyl's theorem survives for polynomials of operators and under quasinilpotent or compact perturbations. First, we show that if T is reduced by each of its finite-dimensional eigenspaces then the Weyl spectrum obeys the spectral mapping theorem, and further if T is reduction-isoloid...
Weyl type theorem for operator matrices
Using topological uniform descent, we give necessary and sufficient conditions for Browder's theorem and Weyl's theorem to hold for an operator A. The two theorems are liable to fail for 2 × 2 operator matrices. In this paper, we explore how they survive for 2 × 2 operator matrices on a Hilbert space.
Weyl type theorems for p-hyponormal and M-hyponormal operators
"Generalized Weyl's theorem holds" for an operator when the complement in the spectrum of the B-Weyl spectrum coincides with the isolated points of the spectrum which are eigenvalues; and "generalized a-Weyl's theorem holds" for an operator when the complement in the approximate point spectrum of the semi-B-essential approximate point spectrum coincides with the isolated points of the approximate point spectrum which are eigenvalues. If T or T* is p-hyponormal or M-hyponormal then for every f ∈...
Weyl type theorems for polaroid operators.
Weyl's and Browder's theorems for operators satisfying the SVEP
We study Weyl's and Browder's theorem for an operator T on a Banach space such that T or its adjoint has the single-valued extension property. We establish the spectral mapping theorem for the Weyl spectrum, and we show that Browder's theorem holds for f(T) for every f ∈ 𝓗 (σ(T)). Also, we give necessary and sufficient conditions for such T to obey Weyl's theorem. Weyl's theorem in an important class of Banach space operators is also studied.
Weyl's theorem, a-Weyl's theorem and single-valued extension property.
In this paper we investigate the relation of Weyl's theorem, of a-Weyl's theorem and the single valued extension property. In particular, we establish necessary and sufficient conditions for a Banch space operator T to satisfy Weyl's theorem or a-Weyl's theorem, in the case in which T, or its dual T*, has the single valued extension property. These results improve similar results obtained by Curto and Han, Djordjevic S. V., Duggal B. P., and Y. M. Han. The theory is exemplified in the case of multipliers...
Weyl's Theorem for a Generalized Derivation and an Elementary Operator
Weyl's theorems and continuity of spectra in the class of p-hyponormal operators
We show that p-hyponormal operators obey Weyl's and a-Weyl's theorem. Also, we show that the spectrum, Weyl spectrum, Browder spectrum and approximate point spectrum are continuous functions in the class of all p-hyponormal operators.
Weyl's theorems and Kato spectrum.
Weyl's type theorems and perturbations.