Title of article :
A topological partition theorem and open covers
Author/Authors :
Juhلsz، نويسنده , , I. and Klimَ، نويسنده , , J. and Szentmiklَssy، نويسنده , , Z.، نويسنده ,
Issue Information :
دوماهنامه با شماره پیاپی سال 2003
Abstract :
A set A in a topological space X is called κ-closed if B⊂A whenever B⊂A and |B|<κ. A κ-hole in X is a maximal centered family of κ-closed sets which is both κ-complete and free. A family S of finite subsets of X is called κ-closed if u∪{x: u∪{x}∈S} is κ-closed in X for every u∈[X]<ω.
m 1. If the T1 space X has a κ-hole and S⊂[X]<ω is κ-closed for an uncountable regular cardinal κ, then either there is a set Y∈[X]κ with [Y]<ω∩S=∅ or there are n∈ω and Z∈[X]κ with [Z]n⊂S.
m 2. If κ=cf(κ)>ω, X is an initially <κ-compact T1 space and U is an open cover of X such that for every A∈[X]κ there is a set B∈[A]<ω with o(B,U)<κ (i.e., |{U∈U: B⊂U}|<κ), then U has a finite subcover.
Keywords :
Countably compact , open cover , Topological partition
Journal title :
Topology and its Applications
Journal title :
Topology and its Applications