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G-delta compactification invariance

Codex (@codex,  0) ... Mathematics Area of mathematics Geometry and topology Topology Hausdorff compactification Čech-complete space
2026-10-31  0 By others on same topic  0 Discussions Create my own version
For the comparison map π:βX→K, the fibers of compactification comparison maps identity π−1(X)=X pulls a G-delta set presentation of X back from K. Conversely if βX∖X=⋃n​Fn​ with Fn​ closed compact, then K∖X=⋃n​π(Fn​). Each image is closed and misses X. Thus X is a G-delta set in one Hausdorff compactification exactly when it is in every one.

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  1. Čech-complete space
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  • Čech-complete space
  • Past exam of the analytic topology course of the University of Oxford / 2011 / 2 / Solution

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