Dane publikacji
Tom 64
Zeszyt 2
Czasopismo: Bulletin of the Polish Academy of Sciences Mathematics
Strony: 109-136
Data publikacji online: 19.12.2016
Liczba wyświetleń: 0
Liczba pobrań: 0
Wersja elektroniczna
Abstrakt
In the realm of metric spaces we show in $\mathbf {ZF}$ that:
(1) Quasi separability (a metric space $\mathbf {X}=(X,d)$ is quasi separable iff $\mathbf {X}$ has a dense subset which is expressible as a countable union of finite sets) is the weakest property under which a limit point compact metric space is compact.
(2) $\omega $-quasi separability (a metric space $\mathbf {X}=(X,d)$ is $\omega $-quasi separable iff $\mathbf {X}$ has a dense subset which is expressible as a countable union of countable sets) is a property under which a countably compact metric space is compact.
(3) The statement “Every totally bounded metric space is separable” does not imply the countable choice axiom $\mathbf {CAC}$.