Generalizations of Kaplansky's Theorem Involving Unbounded Linear Operators
We are mainly concerned with the result of Kaplansky on the composition of two normal operators in the case in which at least one of the operators is unbounded.
Generalized boundary value problems with abstract side conditions and their adjoints. II
Generalized couplings
Generalized densities and distributional adjoints of natural operators.
Generalized inverses in C*-algebras II
Commutativity and continuity conditions for the Moore-Penrose inverse and the "conorm" are established in a C*-algebra; moreover, spectral permanence and B*-properties for the conorm are proved.
Geometric, spectral and asymptotic properties of averaged products of projections in Banach spaces
According to the von Neumann-Halperin and Lapidus theorems, in a Hilbert space the iterates of products or, respectively, of convex combinations of orthoprojections are strongly convergent. We extend these results to the iterates of convex combinations of products of some projections in a complex Banach space. The latter is assumed uniformly convex or uniformly smooth for the orthoprojections, or reflexive for more special projections, in particular, for the hermitian ones. In all cases the proof...
Geometry of the spectral semidistance in Banach algebras
Let be a unital Banach algebra over , and suppose that the nonzero spectral values of and are discrete sets which cluster at , if anywhere. We develop a plane geometric formula for the spectral semidistance of and which depends on the two spectra, and the orthogonality relationships between the corresponding sets of Riesz projections associated with the nonzero spectral values. Extending a result of Brits and Raubenheimer, we further show that and are quasinilpotent equivalent if...
Green's formula for right invertible operators
Grüss type inequalities for forward difference of vectors in inner product spaces.
Hilberträume mit amorphen basen
Imagen de un sistema ortogonal completo de rayos por un operador lineal acotado.
Interchangeability of unbounded linear operators: General theory of transmutativity
Invariance properties of an operator product involving generalized inverses.
Inverses et propriétés spectrales des matrices de Toeplitz à symbole singulier
Invertibility of matrix Wiener--Hopf plus Hankel operators with APW Fourier symbols.
Invertibility of the commutator of an element in a C*-algebra and its Moore-Penrose inverse
We study the subset in a unital C*-algebra composed of elements a such that is invertible, where denotes the Moore-Penrose inverse of a. A distinguished subset of this set is also investigated. Furthermore we study sequences of elements belonging to the aforementioned subsets.
Iterated series and the Hellinger-Toeplitz theorem.
We show that an iterated double series condition due to Antosik implies the uniform convergence of the double series. An application of Antosik's condition is given to the derivation of a vector form of the Hellinger-Toeplitz theorem.
Kato-Protter type inequalities, bounded vectors and the exponential function
Linear contraction mappings
Linear fractional transformations and companion matrices