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Compact Metric Spaces and Weak Forms of the Axiom of Choice
Authors:Kyriakos Keremedis  Eleftherios Tachtsis
Abstract:It is shown that for compact metric spaces (X, d) the following statements are pairwise equivalent: “X is Loeb”, “X is separable”, “X has a we ordered dense subset”, “X is second countable”, and “X has a dense set G = ∪{Gn : nω}, ∣Gn∣ < ω, with limn→∞ diam (G n) = 0”. Further, it is shown that the statement: “Compact metric spaces are weakly Loeb” is not provable in ZF0 , the Zermelo‐Fraenkel set theory without the axiom of regularity, and that the countable axiom of choice for families of finite sets CACfin does not imply the statement “Compact metric spaces are separable”.
Keywords:Countable axiom of choice for families of finite sets  Countable axiom of choice  Countable axiom of multiple choice  Compact metric space  Loeb metric space  Weakly Loeb metric space  Separable metric space  Second countable metric space
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