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Mostrando ítems 11-20 de 57
Artículo
Invariant subspaces of parabolic self-maps in the Hardy space
(International Press, 2010-01)
It is shown that the lattice of invariant subspaces of the operator of multiplication by a cyclic element of a Banach algebra consists of the closed ideals of this algebra. As an application, with the help of some elements ...
Artículo
Geodesic Ptolemy spaces and fixed points
(Elsevier, 2011-01-01)
We prove that geodesic Ptolemy spaces with a continuous midpoint map are strictly convex. Moreover, we show that geodesic Ptolemy spaces with a uniformly continuous midpoint map are reflexive and that in such a setting ...
Artículo
Weakly coercive mappings sharing a value
(Academy of Sciences of Czech Republic, Mathematical Institute, 2011)
Some sufficient conditions are provided that guarantee that the difference of a compact mapping and a proper mapping defined between any two Banach spaces over K has at least one zero. When conditions are strengthened, ...
Artículo
The fixed point property and unbounded sets in CAT(0) spaces
(Elsevier, 2013-12-15)
In this work we study the fixed point property for nonexpansive self-mappings defined on convex and closed subsets of a CAT(0) space. We will show that a positive answer to this problem is very much linked with the Euclidean ...
Artículo
Hardy-Littlewood inequalities for norms of positive operators on sequence spaces
(Elsevier, 2013-01-01)
We consider estimates of Hardy and Littlewood for norms of operators on sequence spaces, and we apply a factorization result of Maurey to obtain improved estimates and simplified proofs for the special case of a positive operator.
Artículo
Some examples of matrix-valued orthogonal functions having a differential and an integral operator as eigenfunctions
(Elsevier, 2011-05)
The aim of this paper is to show some examples of matrix-valued orthogonal functions on the real line which are simultaneously eigenfunctions of a second-order differential operator of Schrödinger type and an integral ...
Artículo
A fixed point theorem for weakly Zamfirescu mappings
(Elsevier, 2011-03-01)
In [13] T. Zamfirescu, Fixed point theorems in metric spaces, Arch. Math. 23 (1972), 292–298. Zamfirescu gave a fixed point theorem that generalizes the classical fixed point theorems by Banach, Kannan and Chatterjea. In ...
Artículo
Vector spaces of non-extendable holomorphic functions
(Springer, 2018-02)
In this paper, the linear structure of the family He(G) of holomorphic functions in a domain G of the complex plane that are not analytically continuable beyond the boundary of G is analyzed. We prove that He(G) contains, ...
Artículo
Function algebras with a strongly precompact unit ball
(Elsevier, 2013-10-01)
Let µ be a finite positive Borel measure with compact support K ⊆ C, and regard L∞(µ) as an algebra of multiplication operators on the Hilbert space L2(µ). Then consider the subalgebra A(K) of all continuous functions on ...
Artículo
Density of the set of renormings in c0 without asymptotically isometric copies of c0 and failing to have the fixed point property
(Casa Cărţii de Ştiinţă Cluj-Napoca, 2013)
It is proved that the family of all equivalent norms in c0 without asymptotically isometric copies of c0 and failing to have the fixed point property is dense in the set of all renormings of c0.