Hostname: page-component-848d4c4894-p2v8j Total loading time: 0 Render date: 2024-05-07T18:15:57.584Z Has data issue: false hasContentIssue false

Perfect Mappings and Spaces of Countable Type

Published online by Cambridge University Press:  20 November 2018

J. E. Vaughan*
Affiliation:
The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
Rights & Permissions [Opens in a new window]

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

In [1, p. 41, Theorem 3.10] Arhangel'skiï proved that the perfect image of a completely regular space of countable type is of countable type, and he asked [1, p. 60, problem 4] if a similar result held for regular or Hausdorff spaces. In this paper, it is proved that the perfect image of a space of countable type is of countable type, provided that the image is Hausdorff or regular. An affirmative answer to both of Arhangel'skiï's questions follows immediately from this. Arhangel'skiï made use of the Stone-Čech compactification in the proof of his result, but the proofs below are of a different nature.

Let X be a topological space and let KX. A collection of open sets is called a base at K provided that for every open set WK there exists such that KUW. Clearly, we may assume that every member of contains K.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1970

References

1. Arhangel'skiï, A. V., Bicompact sets and the topology of spaces, Trans. Moscow Math. Soc. 13 (1965), 162 ( = Trudy Moskov. Mat. Obsc. 13 (1965), 3-55).Google Scholar