Title of article :
Subspaces of connected spaces
Author/Authors :
Porter، نويسنده , , Jack R. and Woods، نويسنده , , R.Grant، نويسنده ,
Issue Information :
دوماهنامه با شماره پیاپی سال 1996
Abstract :
A connectification of a topological space X is a connected Hausdorff space that contains X as a dense subspace. Watson and Wilson have noted that a Hausdorff space with a connectification has no nonempty proper clopen H-closed subspaces. Here it is proven that a Hausdorff space in which every nonempty proper clopen set is not feebly compact and the cardinality of the set of clopen sets is at most 2c is connectifiable. This result is used to show that every metric space with no nonempty proper clopen H-closed subspace is connectifiable, answering a question asked by Watson and Wilson. Also, there is a nonconnectifiable, Hausdorff space of cardinality c with no proper H-closed subspace. Using the set-theoretic hypothesis p = c, an example of a nonconnectifiable, normal Hausdorff space of cardinality c is constructed which has no nonempty compact open subset. This space is locally compact at all but one point, and if the continuum hypothesis is assumed it is first countable. This space provides a solution to questions asked by Watson and Wilson as well as Mack. The paper concludes by examining when extremally disconnected Tychonoff spaces have Tychonoff connectifications.
Keywords :
Connected , H-closed , Hausdorff extension
Journal title :
Topology and its Applications
Journal title :
Topology and its Applications