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Matt N.
11:51 AM
Quick question about well-orders:
If I have a set $S$ and a bijection $f: \mathbb N \to S$, but not necessarily order-preserving: is $S$ well-ordered?
Or put differently:
Is every set in bijection with a well-ordered set well-ordered?
Matt N.
12:35 PM
Yes.
Let $S$ be in bijection with a well odered set $W$ with $f: S \to W$. Define a well-order on $S$ as $s_1 \leq s_2 \iff f(s_1) \leq f(s_2)$.
Matt N.
1:34 PM
Then show that this defines a well-order on $S$.
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