On some notions related to compactness for locales
This paper deals with the behavior of -spaces, countably bi-quasi--spaces and singly bi-quasi--spaces with point-countable -systems. For example, we show that every -space with a point-countable -system is locally compact paracompact, and every separable singly bi-quasi--space with a point-countable -system has a countable -system. Also, we consider equivalent relations among spaces entried in Table 1 in Michael’s paper [15] when the spaces have point-countable -systems.
A sufficient condition that the product of two compact spaces has the property of weak approximation by points (briefly WAP) is given. It follows that the product of the unit interval with a compact WAP space is also a WAP space.
We prove a number of results on star covering properties which may be regarded as either generalizations or specializations of topological properties related to the ones mentioned in the title of the paper. For instance, we give a new, entirely combinatorial proof of the fact that -spaces constructed from infinite almost disjoint families are not star-compact. By going a little further we conclude that if is a star-compact space within a certain class, then is neither first countable nor separable....
A space is -starcompact if for every open cover of there exists a Lindelöf subset of such that We clarify the relations between -starcompact spaces and other related spaces and investigate topological properties of -starcompact spaces. A question of Hiremath is answered.
A space is -starcompact if for every open cover of there exists a countably compact subset of such that In this paper we investigate the relations between -starcompact spaces and other related spaces, and also study topological properties of -starcompact spaces.