Universally Kuratowski–Ulam spaces
Fundamenta Mathematicae, Tome 165 (2000) no. 3, pp. 239-247.

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We introduce the notions of Kuratowski-Ulam pairs of topological spaces and universally Kuratowski-Ulam space. A pair (X,Y) of topological spaces is called a Kuratowski-Ulam pair if the Kuratowski-Ulam Theorem holds in X× Y. A space Y is called a universally Kuratowski-Ulam (uK-U) space if (X,Y) is a Kuratowski-Ulam pair for every space X. Obviously, every meager in itself space is uK-U. Moreover, it is known that every space with a countable π-basis is uK-U. We prove the following:  • every dyadic space (in fact, any continuous image of any product of separable metrizable spaces) is uK-U (so there are uK-U Baire spaces which do not have countable π-bases);  • every Baire uK-U space is ccc.
DOI : 10.4064/fm-165-3-239-247
Keywords: Baire space, dyadic space, quasi-dyadic space, Kuratowski-Ulam Theorem, Kuratowski-Ulam pair, universally Kuratowski-Ulam space

David Fremlin 1 ; Tomasz Natkaniec 1 ; Ireneusz Recław 1

1
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David Fremlin; Tomasz Natkaniec; Ireneusz Recław. Universally Kuratowski–Ulam spaces. Fundamenta Mathematicae, Tome 165 (2000) no. 3, pp. 239-247. doi : 10.4064/fm-165-3-239-247. http://geodesic.mathdoc.fr/articles/10.4064/fm-165-3-239-247/

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