International Journal of Mathematics and Mathematical Sciences
Volume 26 (2001), Issue 12, Pages 745-751
doi:10.1155/S0161171201005889

Countably I-Compact Spaces

Abstract

We introduce the class of countably I-compact spaces as a proper subclass of countably S-closed spaces. A topological space (X,T) is called countably I-compact if every countable cover of X by regular closed subsets contains a finite subfamily whose interiors cover X. It is shown that a space is countably I-compact if and only if it is extremally disconnected and countably S-closed. Other characterizations are given in terms of covers by semiopen subsets and other types of subsets. We also show that countable I-compactness is invariant under almost open semi-continuous surjections.