List questions from ordinals

Published on 25 Mar 2026 - 20:35

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Applying a function ordinal number of times

Published on 12 Sep 2016 - 21:22

172

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A notion of iterated consistency axioms

Published on 25 Mar 2026 - 19:03

224

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uncountable union of uncountable sets and the usage of the axiom of choice

Published on 26 Sep 2016 - 5:28

589

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What does it mean for a well ordering to have length ω? ω^ω?

Published on 05 Oct 2016 - 6:47

90

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predicate for admissible ordinals

Published on 08 Oct 2016 - 21:23

200

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$\omega_{\alpha+1}$ is a projection of $\wp(\omega_{\alpha})$

Published on 12 Oct 2016 - 7:51

209

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Well-ordered sets in the field of Hahn series

Published on 25 Mar 2026 - 21:22

712

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Countable ordinals in the reals

Published on 15 Oct 2016 - 21:26

309

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Unions of ordinals and their suprema

Published on 16 Oct 2016 - 20:14

634

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For every ordinal $\alpha$, there is a cardinal number greater than $\alpha$ without AC

Published on 26 Mar 2026 - 14:25

160

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Show that $\Gamma(\alpha\times\alpha)\leq\omega^{\alpha}$.

Published on 24 Oct 2016 - 19:30

1.1k

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If $\alpha\ne\beta$ are ordinals and $\alpha\subset\beta$ show $\alpha\in\beta$

Published on 25 Oct 2016 - 4:44

533

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Show an increasing function f from omega_1 to R is eventually constant

Published on 06 Nov 2016 - 16:02

180

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Induction, coinduction, and ordinal induction

Published on 25 Mar 2026 - 7:47

List Question

Puzzle about throwing two darts at the first uncountable ordinal.

Applying a function ordinal number of times

A notion of iterated consistency axioms

uncountable union of uncountable sets and the usage of the axiom of choice

What does it mean for a well ordering to have length ω? ω^ω?

predicate for admissible ordinals

$\omega_{\alpha+1}$ is a projection of $\wp(\omega_{\alpha})$

Well-ordered sets in the field of Hahn series

Countable ordinals in the reals

Unions of ordinals and their suprema

For every ordinal $\alpha$, there is a cardinal number greater than $\alpha$ without AC

Show that $\Gamma(\alpha\times\alpha)\leq\omega^{\alpha}$.

If $\alpha\ne\beta$ are ordinals and $\alpha\subset\beta$ show $\alpha\in\beta$

Show an increasing function f from omega_1 to R is eventually constant

Induction, coinduction, and ordinal induction

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