In this paper, we show the representation of Köthe dual of Banach sequence spaces ${\ell }_p\left[X\right]$$(1\le p<\infty )...$

In this paper we consider some matrix operators on block weighted sequence spaces $l_p(w,F)$. The problem is to find the lower bound of some matrix operators such as Hausdorff and Hilbert matrices on $l_p(w,F)$. This study is an extension of papers by G. Bennett, G.J.O. Jameson and R. Lashkaripour.

A generalization of the Lyapunov convexity theorem is proved for a vector measure with values in a Banach space with unconditional basis, which is q-concave for some q < ∞ and does not contain any isomorphic copy of l₂.

If $E=e_i$ and $F=f_i$ are two 1-unconditional basic sequences in L₁ with E r-concave and F p-convex, for some 1 ≤ r < p ≤ 2, then the space of matrices $a_{i,j}$ with norm $\left|\right|a_{i,j}{\left|\right|}_{E\left(F\right)}=\left|\right|{\sum }_k\left|\right|{\sum }_l{a}_{k,l}{f}_l\left|\right|e_k\left|\right|$ embeds into L₁. This generalizes a recent result of Prochno and Schütt.

We study minimality properties of partly modified mixed Tsirelson spaces. A Banach space with a normalized basis $\left(e_k\right)$ is said to be subsequentially minimal if for every normalized block basis $\left(x_k\right)$ of $\left(e_k\right)$, there is a further block basis $\left(y_k\right)$ of $\left(x_k\right)$ such that $\left(y_k\right)$ is equivalent to a subsequence of $\left(e_k\right)$. Sufficient conditions are given for a partly modified mixed Tsirelson space to be subsequentially minimal, and connections with Bourgain’s ℓ¹-index are established. It is also shown that a large class of mixed Tsirelson...

We establish Hölder-type inequalities for Lorentz sequence spaces and their duals. In order to achieve these and some related inequalities, we study diagonal multilinear forms in general sequence spaces, and obtain estimates for their norms. We also consider norms of multilinear forms in different Banach multilinear ideals.

The aim of this paper is to discuss the concept of near smoothness in some Banach sequence spaces.

In 1972, the late B. E. Johnson introduced the notion of an amenable Banach algebra and asked whether the Banach algebra ℬ(E) of all bounded linear operators on a Banach space E could ever be amenable if dim E = ∞. Somewhat surprisingly, this question was answered positively only very recently as a by-product of the Argyros-Haydon result that solves the “scalar plus compact problem”: there is an infinite-dimensional Banach space E, the dual of which is ℓ¹, such that $ℬ\left(E\right)=\left(E\right)+ℂi{d}_E$. Still, ℬ(ℓ²) is not amenable,...

Let be the class of Banach spaces X for which every weakly quasi-continuous mapping f: A → X defined on an α-favorable space A is norm continuous at the points of a dense $G_{\delta }$ subset of A. We will show that this class is stable under c₀-sums and ${\ell }^p$-sums of Banach spaces for 1 ≤ p < ∞.

The notion of a measure of noncompactness turns out to be a very important and useful tool in many branches of mathematical analysis. The current state of this theory and its applications are presented in the books [1,4,11] for example.The notion of a measure of weak noncompactness was introduced by De Blasi [8] and was subsequently used in numerous branches of functional analysis and the theory of differential and integral equations (cf. [2,3,9,10,11], for instance).In this note we summarize our...

Let D be the open unit disc and μ a positive bounded measure on [0,1]. Extending results of Mateljević/Pavlović and Shields/Williams we give Banach-space descriptions of the classes of all harmonic (holomorphic) functions f: D → ℂ satisfying ${ʃ}_0^1({ʃ}_0^{2\pi }|f\left(r{e}^{i\phi }\right){{|}^{p}d\phi )}^{q/p}d\mu \left(r\right)<\infty$.