We give a characterization of Banach spaces X containing a subspace with a shrinking Markushevich basis {xγ , fγ}γ∈Γ. This gives a sufficient condition for X to have a renorming with Mazur’s intersection property. A biorthogonal system in a Banach space X is a subset {xγ , fγ}γ∈Γ ⊂ X×X such that fγ(xγ′) = δγγ′ for γ, γ ′ ∈ Γ. The biorthogonal system {xγ, fγ}γ∈Γ in X is called fundamental if X =...

We consider a nite or in nite family of closed convex sets with nonempty intersection in a normed space A property relating their epigraphs with their intersection s epigraph is studied and its relations to other constraint quali cations such as the linear regularity the strong CHIP and Jameson s G property are estab lished With suitable continuity assumption we show how this property can be en...

K. S. Lau had shown that a reflexive Banach space has the Mazur Intersection Property (MIP) if and only if every closed bounded convex set is the closed convex hull of its farthest points. In this work, we show that in general this latter property is equivalent to a property stronger than the MIP. As corollaries, we recapture the result of Lau and characterize the w*-MIP in dual of RNP spaces.

The main result of the present note states that it is consistent with the ZFC axioms of set theory (relying on Martin’s Maximum MM axiom), that every Asplund space of density character ω1 has a renorming with the Mazur intersection property. Combined with the previous result of Jiménez and Moreno (based upon the work of Kunen under the continuum hypothesis) we obtain that the MIP renormability ...

‎in 1970‎, ‎menegazzo [gruppi nei quali ogni sottogruppo e intersezione di sottogruppi massimali‎, ‎ atti accad‎. ‎naz‎. ‎lincei rend‎. ‎cl‎. ‎sci‎. ‎fis‎. ‎mat‎. ‎natur. 48 (1970)‎, ‎559--562.] gave a complete description of the structure of soluble $im$-groups‎, ‎i.e.‎, ‎groups in which every subgroup can be obtained as intersection of maximal subgroups‎. ‎a group $g$ is said to have the $fm$...

Helly’s theorem is one of the fundamental results in discrete geometry [9]. It states that if every 6 d+1 sets in a set system S of convex sets in R have non-empty intersection then all of the sets in S have non-empty intersection. Equivalently, if the entire family S has empty intersection, then there is a subset S ′ ⊂ S (a witness) of size 6 d+1 which also has empty intersection. Over the yea...

The notions of (strong) intersection-soft filters in R 0 -algebras are introduced, and related properties are investigated. Characterizations of a (strong) intersection-soft filter are established, and a new intersection-soft filter from old one is constructed. A condition for an intersection-soft filter to be strong is given, and an extension property of a strong intersection-soft filter is es...