Geodesic
On open maps of Borel sets
Fundamenta Mathematicae, Tome 146 (1994) no. 3, pp. 203-213

Voir la notice de l'article provenant de la source Institute of Mathematics Polish Academy of Sciences

We answer in the affirmative [Th. 3 or Corollary 1] the question of L. V. Keldysh [5, p. 648]: can every Borel set X lying in the space of irrational numbers ℙ not $G_δ · F_σ$ and of the second category in itself be mapped onto an arbitrary analytic set Y ⊂ ℙ of the second category in itself by an open map? Note that under a space of the second category in itself Keldysh understood a Baire space. The answer to the question as stated is negative if X is Baire but Y is not Baire.
DOI : 10.4064/fm-146-3-203-213
Keywords: open maps, Borel sets, analytic sets, space of the first category, space of the second category, Baire space

A. Ostrovsky 1

1 
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A. Ostrovsky. On open maps of Borel sets. Fundamenta Mathematicae, Tome 146 (1994) no. 3, pp. 203-213. doi: 10.4064/fm-146-3-203-213

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