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Sune Jakobsen
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(Edit: The first formulation is wrong. See the second answer) Does every totally ordered set contain an unbounded countable subset. In other words: If S is a totally ordered set, can we find a (edit: at most) countable subset A, such that for every $s \in S$, there is a $a \in A, a\geq s$?

Does every totally ordered set contain an unbounded countable subset. In other words: If S is a totally ordered set, can we find a countable subset A, such that for every $s \in S$, there is a $a \in A, a\geq s$?

(Edit: The first formulation is wrong. See the second answer) Does every totally ordered set contain an unbounded countable subset. In other words: If S is a totally ordered set, can we find a (edit: at most) countable subset A, such that for every $s \in S$, there is a $a \in A, a\geq s$?

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Sune Jakobsen
  • 1.6k
  • 2
  • 18
  • 30

Unbounded countable subset

Does every totally ordered set contain an unbounded countable subset. In other words: If S is a totally ordered set, can we find a countable subset A, such that for every $s \in S$, there is a $a \in A, a\geq s$?