A theorem on B-splines
A theorem on isotropic spaces
Let X be a normed space and the group of all linear surjective isometries of X that are finite-dimensional perturbations of the identity. We prove that if acts transitively on the unit sphere then X must be an inner product space.
A theorem on matrices and its applications in functional analysis
A theory of Besov and Triebel-Lizorkin spaces on metric measure spaces modeled on Carnot-Carathéodory spaces.
A unified approach for commutators theorems in interpolation theory, a survey.
We review the main facts that are behind a unified construction for the commutator theorem of the main interpolation methods.
A unified approach to the strong approximation property and the weak bounded approximation property of Banach spaces
We consider convex versions of the strong approximation property and the weak bounded approximation property and develop a unified approach to their treatment introducing the inner and outer Λ-bounded approximation properties for a pair consisting of an operator ideal and a space ideal. We characterize this type of properties in a general setting and, using the isometric DFJP-factorization of operator ideals, provide a range of examples for this characterization, eventually answering a question...
A uniformly convex Banach space which contains no
A universal Lipschitz extension property of Gromov hyperbolic spaces.
A universal modulus for normed spaces
We define a handy new modulus for normed spaces. More precisely, given any normed space X, we define in a canonical way a function ξ:[0,1)→ ℝ which depends only on the two-dimensional subspaces of X. We show that this function is strictly increasing and convex, and that its behaviour is intimately connected with the geometry of X. In particular, ξ tells us whether or not X is uniformly smooth, uniformly convex, uniformly non-square or an inner product space.
A universal non-compact operator
A Universal Topology for Sequence Spaces.
A weakly pseudocompact subspace of Banach space is weakly compact
A₁-regularity and boundedness of Calderón-Zygmund operators
The Coifman-Fefferman inequality implies quite easily that a Calderón-Zygmund operator T acts boundedly in a Banach lattice X on ℝⁿ if the Hardy-Littlewood maximal operator M is bounded in both X and X'. We establish a converse result under the assumption that X has the Fatou property and X is p-convex and q-concave with some 1 < p, q < ∞: if a linear operator T is bounded in X and T is nondegenerate in a certain sense (for example, if T is a Riesz transform) then M is bounded in both X and...
About an example of a Banach space not weaky K-analytic.
About certain isomorphic properties of Banach spaces in projective tensor products.
This note is an announcement of results contained in the papers [4], [5], [6] concerning isomorphic properties of Banach spaces in projective tensor products (for this definition and some property we refer to [1]). At the end, some new result is obtained too.
About interpolation of subspaces of rearrangement invariant spaces generated by Rademacher system.
About some parameters of normed linear spaces
Si prendono in considerazione particolari costanti relative alla struttura della sfera unitaria di uno spazio di Banach. Se ne studiano alcune generali proprietà, con particolare riferimento alle relazioni con il modulo di convessità dello spazio. Se ne fornisce inoltre una esatta valutazione negli spazi .
About the Banach envelope of l1,∞.
About the class of ordered limited operators
We give a brief survey of recent results of order limited operators related to some properties on Banach lattices.
Absolutely (∞,p) summing and weakly-p-compact operators in Banach spaces.
A sequence (xn) in a Banach space X is said to be weakly-p-summable, 1 ≤ p < ∞, when for each x* ∈ X*, (x*xn) ∈ lp. We shall say that a sequence (xn) is weakly-p-convergent if for some x ∈ X, (xn - x) is weakly-p-summable.