English

Scattered compact sets in continuous images of \v{C}ech-complete spaces

General Topology 2021-11-01 v2

Abstract

Assume hat a functionally Hausdorff space XX is a continuous image of a \v{C}ech complete space PP with Lindel\"of number l(P)<cl(P)<\mathfrak c. Then the following conditions are equivalent: (i) every compact subset of XX is scattered, (ii) for every continuous map f:XYf:X\to Y to a functionally Hausdorff space YY the image f(X)f(X) has cardinality f(X)max{l(P),ψ(Y)}|f(X)|\le \max\{l(P),\psi(Y)\}, (iii) no continuous map f:X[0,1]f:X\to[0,1] is surjective. Also we prove the equivalence of the conditions: (a) ω1<b\omega_1<\mathfrak b, (b) a K-analytic space XX (with a unique non-isolated point) is countable if and only if every compact subset of XX is countable.

Keywords

Cite

@article{arxiv.1904.08969,
  title  = {Scattered compact sets in continuous images of \v{C}ech-complete spaces},
  author = {Taras Banakh and Bogdan Bokalo and Vladimir Tkachuk},
  journal= {arXiv preprint arXiv:1904.08969},
  year   = {2021}
}

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5 pages