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Two new equivalents of Lindelöf metric spaces
Abstract:In the realm of Lindelöf metric spaces the following results are obtained in urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0001: (i) If urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0002 is a Lindelöf metric space then it is both densely Lindelöf and almost Lindelöf. In addition, under the countable axiom of choice urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0003, the three notions coincide. (ii) The statement “every separable metric space is almost Lindelöf” implies that every infinite subset of urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0004 has a countably infinite subset). (iii) The statement “every almost Lindelöf metric space urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0005 is quasi totally bounded implies urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0006. (iv) The proposition “every quasi totally bounded metric space is separable” lies, in the deductive hierarchy of choice principles, strictly between the countable union theorem urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0007 and urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0008. Likewise, the statement “every pre‐Lindelöf (or Lindelöf) metric space is separable” lies strictly between urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0009 and urn:x-wiley:09425616:media:malq201600059:malq201600059-math-0010.
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