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Results tagged with transfinite-induction
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user 479330
2
votes
Diagonalization over a normal function and its derivatives on transfinite ordinals
No, not all $G_\beta$ are normal. For example let $\Phi(0,\beta)$ be any normal function whose least fixed point is greater than $\omega$ and consider $G_\omega(\alpha)$. Since $\Phi(\beta+1,0)>\omeg …
- 2,031
2
votes
What's the use of countable ordinals? (prompted by a remark of Tim Gowers)
As mentioned in Prof. Weaver's answer, the graph minor theorem (also known as the Robertson-Seymour theorem) uses large countable ordinals. The graph minor theorem is quite relevant to non-set-theoret …
- 2,031