Displaying similar documents to “On bicompacta which are unions of two subspaces of a certain type”

Mapping theorems on countable tightness and a question of F. Siwiec

Shou Lin, Jinhuang Zhang (2014)

Commentationes Mathematicae Universitatis Carolinae

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In this paper s s -quotient maps and s s q -spaces are introduced. It is shown that (1) countable tightness is characterized by s s -quotient maps and quotient maps; (2) a space has countable tightness if and only if it is a countably bi-quotient image of a locally countable space, which gives an answer for a question posed by F. Siwiec in 1975; (3) s s q -spaces are characterized as the s s -quotient images of metric spaces; (4) assuming 2 ω < 2 ω 1 , a compact T 2 -space is an s s q -space if and only if every countably...