A decomposition property of weak Lî

Let be a set of disjointly supported, positive functions in the Banach envelope of weak L1. We prove that each fi can be written as ei + gi where ei and gi, are disjointly supported and satisfy these additional properties: the ei's are isometrically the basis in the envelope norm; the envelope norm of a linear combination of the gi's is equal to the envelope norm of the corresponding combination of the fi's.

Banach Envelopes of Non-Locally Convex Spaces

Let X be a quasi-Banach space whose dual X* separates the points of X. Then X* is a Banach space under the normFrom X we can construct the Banach envelope Xc of X by defining for x ∊ X, the normThen Xc is the completion of (X, ‖ ‖c). Alternatively ‖ ‖c is the Minkowski functional of the convex hull of the unit ball. Xc has the property that any bounded linear operator L:X → Z into a Banach space extends with preservation of norm to an operator .