On cardinal invariants
Archangelskij, A. V.
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Displaying similar documents to “Totally proper forcing and the Moore-Mrówka problem”
On cardinal invariants
Sequential compactness vs. countable compactness
Angelo Bella, Peter Nyikos (2010)
Colloquium Mathematicae
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The general question of when a countably compact topological space is sequentially compact, or has a nontrivial convergent sequence, is studied from the viewpoint of basic cardinal invariants and small uncountable cardinals. It is shown that the small uncountable cardinal 𝔥 is both the least cardinality and the least net weight of a countably compact space that is not sequentially compact, and that it is also the least hereditary Lindelöf degree in most published models. Similar results,...
Ordinal invariants in topology II. Sequential order of compactifications
V. Kannan (1979)
Compositio Mathematica
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Compact C-spaces and S-spaces
Rajagopalan, M.
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On a theorem of Šapirovskiĭ on the size of a sequential space.
Bella, Angelo (2005)
Mathematica Pannonica
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On bicompacta which are unions of two subspaces of a certain type
Aleksander V. Arhangel'skii (1978)
Commentationes Mathematicae Universitatis Carolinae
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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 -quotient maps and -spaces are introduced. It is shown that (1) countable tightness is characterized by -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) -spaces are characterized as the -quotient images of metric spaces; (4) assuming , a compact -space is an -space if and only if every countably...