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Disjoint unions of topological spaces and choice. (English) Zbl 0922.03069

This paper continues the authors’ paper “Versions of normality and some weak forms of the axiom of choice” [Math. Log. Q. 44, 367-382 (1998; Zbl 0911.03027)] about the set-theoretical strength of theorems which assert that disjoint unions of topological spaces inherit properties from the summands. [Recall for example: The axiom of multiple choice is equivalent to “disjoint unions of normal spaces are normal”.] The main result of the present paper is Theorem 2: The axiom of multiple choice is equivalent to “disjoint unions of paracompact spaces are normal”. Another interesting result is Example 3: The “ordered Mostowski permutation model” satisfies “disjoint unions of metrizable spaces are metrizable”.
Reviewer: N.Brunner (Wien)

MSC:

03E25 Axiom of choice and related propositions
54B15 Quotient spaces, decompositions in general topology
54D10 Lower separation axioms (\(T_0\)–\(T_3\), etc.)
54D20 Noncompact covering properties (paracompact, Lindelöf, etc.)
54D15 Higher separation axioms (completely regular, normal, perfectly or collectionwise normal, etc.)
54E35 Metric spaces, metrizability

Citations:

Zbl 0911.03027
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References:

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