Point-finite collection
Topological concept for collections of sets From Wikipedia, the free encyclopedia
In mathematics, a collection or family of subsets of a topological space is said to be point-finite if every point of lies in only finitely many members of [1][2]
A metacompact space is a topological space in which every open cover admits a point-finite open refinement. Every locally finite collection of subsets of a topological space is also point-finite. A topological space in which every open cover admits a locally finite open refinement is called a paracompact space. Every paracompact space is therefore metacompact.[2]
Dieudonné's theorem
Summarize
Perspective
Theorem—[3][4] A topological space is normal if and only if each point-finite open cover of has a shrinking; that is, if is an open cover indexed by a set , there is an open cover indexed by the same set such that for each .
The original proof uses Zorn's lemma, while Willard uses transfinite recursion.
References
Wikiwand - on
Seamless Wikipedia browsing. On steroids.