On isomorphisms of anisotropic Sobolev spaces with "classical Banach spaces" and a Sobolev type embedding theorem
On James and Jordan-von Neumann constants and the normal structure coefficient of Banach spaces
Some relations between the James (or non-square) constant J(X) and the Jordan-von Neumann constant , and the normal structure coefficient N(X) of Banach spaces X are investigated. Relations between J(X) and J(X*) are given as an answer to a problem of Gao and Lau [16]. Connections between and J(X) are also shown. The normal structure coefficient of a Banach space is estimated by the -constant, which implies that a Banach space with -constant less than 5/4 has the fixed point property.
On l^∞ subspaces of Banach spaces.
We obtain refinement of a result of Partington on Banach spaces containing isomorphic copies of l-∞. Motivated by this result, we prove that Banach spaces containing asymptotically isometric copies of l-∞ must contain isometric copies of l-∞.
On Lindenstrauss-Pełczyński spaces
We consider some stability aspects of the classical problem of extension of C(K)-valued operators. We introduce the class ℒ of Banach spaces of Lindenstrauss-Pełczyński type as those such that every operator from a subspace of c₀ into them can be extended to c₀. We show that all ℒ-spaces are of type but not conversely. Moreover, -spaces will be characterized as those spaces E such that E-valued operators from w*(l₁,c₀)-closed subspaces of l₁ extend to l₁. Regarding examples we will show that...
On minimality and lp-complemented subspaces of Orlicz function spaces.
Several properties of the class of minimal Orlicz function spaces LF are described. In particular, an explicitly defined class of non-trivial minimal functions is shown, which provides concrete examples of Orlicz spaces without complemented copies of F-spaces.
On multilinear generalizations of the concept of nuclear operators
This paper introduces the class of Cohen p-nuclear m-linear operators between Banach spaces. A characterization in terms of Pietsch's domination theorem is proved. The interpretation in terms of factorization gives a factorization theorem similar to Kwapień's factorization theorem for dominated linear operators. Connections with the theory of absolutely summing m-linear operators are established. As a consequence of our results, we show that every Cohen p-nuclear (1 < p ≤ ∞ ) m-linear mapping...
On norm attaining operators acting from to C (S)
On norm attaining operators acting on - spaces
On operators which factor through or c₀
Let 1 < p < ∞. Let X be a subspace of a space Z with a shrinking F.D.D. (Eₙ) which satisfies a block lower-p estimate. Then any bounded linear operator T from X which satisfies an upper-(C,p)-tree estimate factors through a subspace of , where (Fₙ) is a blocking of (Eₙ). In particular, we prove that an operator from (2 < p < ∞) satisfies an upper-(C,p)-tree estimate if and only if it factors through . This gives an answer to a question of W. B. Johnson. We also prove that if X is...
On projections in H¹ and BMO
On Schwartz's C-spaces and Orlicz's O-spaces
On some convexity properties of Musielak-Orlicz spaces
On some geometric properties of certain Köthe sequence spaces
It is proved that if a Kothe sequence space is monotone complete and has the weakly convergent sequence coefficient WCS, then is order continuous. It is shown that a weakly sequentially complete Kothe sequence space is compactly locally uniformly rotund if and only if the norm in is equi-absolutely continuous. The dual of the product space of a sequence of Banach spaces , which is built by using an Orlicz function satisfying the -condition, is computed isometrically (i.e. the exact...
On spreading -sequences in Banach spaces
We introduce and study the spreading-(s) and the spreading-(u) property of a Banach space and their relations. A space has the spreading-(s) property if every normalized weakly null sequence has a subsequence with a spreading model equivalent to the usual basis of ; while it has the spreading-(u) property if every weak Cauchy and non-weakly convergent sequence has a convex block subsequence with a spreading model equivalent to the summing basis of . The main results proved are the following: (a)...
On spreading models in
On Stefan Banach and some of his results.
On subspaces of H¹ isomorphic to H¹
On subspaces of L1 which embed into ...1.
On suprabarrelledness of c0 (Ω, X).
Si Ω es un conjunto no vacío y X es un espacio normado real o complejo, se tiene que, con la norma supremo, el espacio c0 (Ω, X) formado por las funciones f : Ω → X tales que para cada ε > 0 el conjunto {ω ∈ Ω : || f(ω) || > ε} es finito es supratonelado si y sólo si X es supratonelado.
On the class of b-L-weakly and order M-weakly compact operators
In this paper, we introduce and study new concepts of b-L-weakly and order M-weakly compact operators. As consequences, we obtain some characterizations of KB-spaces.