Journal of Symbolic Logic
- J. Symbolic Logic
- Volume 75, Issue 3 (2010), 996-1006.
Products of some special compact spaces and restricted forms of AC
We establish the following results:
1. In ZF (i.e., Zermelo-Fraenkel set theory minus the Axiom of Choice AC), for every set I and for every ordinal number α≥ω, the following statements are equivalent:
a. The Tychonoff product of |α| many non-empty finite discrete subsets of I is compact.
b. The union of |α| many non-empty finite subsets of I is well orderable.
2. The statement: For every infinite set I, every closed subset of the Tychonoff product [0,1]ⁱ which consists of functions with finite support is compact, is not provable in ZF set theory.
3. The statement: For every set I, the principle of dependent choices relativised to I implies the Tychonoff product of countably many non-empty finite discrete subsets of I is compact, is not provable in ZF⁰ (i.e., ZF minus the Axiom of Regularity).
The statement: For every set I, every ℵ₀-sized family of non-empty finite subsets of I has a choice function implies the Tychonoff product of ℵ₀ many non-empty finite discrete subsets of I is compact, is not provable in ZF⁰.
J. Symbolic Logic, Volume 75, Issue 3 (2010), 996-1006.
First available in Project Euclid: 9 July 2010
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Keremedis, Kyriakos; Tachtsis, Eleftherios. Products of some special compact spaces and restricted forms of AC. J. Symbolic Logic 75 (2010), no. 3, 996--1006. doi:10.2178/jsl/1278682212. https://projecteuclid.org/euclid.jsl/1278682212