Dependent Choices and Weak Compactness

Countable Choice and Compactness

We work in set-theory without choice ZF. Denoting by AC(N) the countable axiom of choice, we show in ZF+AC(N) that the closed unit ball of a uniformly convex Banach space is compact in the convex topology (an alternative to the weak topology in ZF). We prove that this ball is (closely) convex-compact in the convex topology. Given a set I, a real number p ≥ 1 (resp. p = 0), and some closed subse...

Weak Compactness of the Set of ε-Extensions

James sequences and Dependent Choices

We prove James’s sequential characterization of (compact) reflexivity in set-theory ZF+DC, where DC is the axiom of Dependent Choices. In turn, James’s criterion implies that every infinite set is Dedekind-infinite, whence it is not provable in ZF. Our proof in ZF+DC of James’ criterion leads us to various notions of reflexivity which are equivalent in ZFC but are not equivalent in ZF. We also ...

Bilateral composition operators on vector-valued Hardy spaces

Let $T$ be a bounded operator on the Banach space $X$ and $ph$ be an analytic self-map of the unit disk $Bbb{D}$‎. ‎We investigate some operator theoretic properties of‎ ‎bilateral composition operator $C_{ph‎, ‎T}‎: ‎f ri T circ f circ ph$ on the vector-valued Hardy space $H^p(X)$ for $1 leq p leq‎ ‎+infty$.‎ ‎Compactness and weak compactness of $C_{ph‎, ‎T}$ on $H^p(X)$‎ ‎are characterized an...

SOME RESULTS ON INTUITIONISTIC FUZZY SPACES

In this paper we define intuitionistic fuzzy metric and normedspaces. We first consider finite dimensional intuitionistic fuzzy normed spacesand prove several theorems about completeness, compactness and weak convergencein these spaces. In section 3 we define the intuitionistic fuzzy quotientnorm and study completeness and review some fundamental theorems. Finally,we consider some properties of...