Question

Should I write these ordinal operations in Cantor normal form?

score 167 · Answer 1 · 2018-07-17 19:41:10

167

Views

Should I write these ordinal operations in Cantor normal form?

Published on 17 Jul 2018 - 19:41

score 70 · Answer 2 · 2018-07-20 00:09:30

70

Views

Show that $A$ or $B$ must be bounded in $\omega_1$

Published on 20 Jul 2018 - 0:09

score 122 · Answer 3 · 2018-07-21 09:26:35

122

Views

How should I write this function $f:\mathcal P_{fin}(\omega^{<\omega})\to \mathcal P_{fin}(\omega^{<\omega})$?

Published on 21 Jul 2018 - 9:26

score 779 · Answer 4 · 2018-07-24 04:01:40

779

Views

Ordinals in category theory?

Published on 24 Jul 2018 - 4:01

score 365 · Answer 5 · 2018-08-04 11:50:56

365

Views

Proving the Bourbaki–Witt Theorem using Recursion.

Published on 04 Aug 2018 - 11:50

score 117 · Answer 6 · 2018-08-10 02:09:46

117

Views

What is the order type of the set of smooth functions ordered by growth rate?

Published on 10 Aug 2018 - 2:09

score 90 · Answer 7 · 2018-08-10 15:08:29

90

Views

When does an injective function $\omega^{<\omega}\to\Bbb N$ have positive density in the integers?

Published on 10 Aug 2018 - 15:08

score 608 · Answer 8 · 2026-03-22 19:24:37

608

Views

Finding a well-ordering of the natural numbers of a given order type

Published on 22 Mar 2026 - 19:24

score 1k · Answer 9 · 2026-03-22 13:26:38

1k

Views

How to formally use transfinite recursion to construct a sequence for a proof of Zorn's lemma

Published on 22 Mar 2026 - 13:26

score 66 · Answer 10 · 2026-03-22 18:01:15

66

Views

Is it possible to construct order types using sets?

Published on 22 Mar 2026 - 18:01

score 158 · Answer 11 · 2026-02-23 06:39:38

158

Views

$\omega_1$ is a limit point of the subset $[0,\omega_1)$

Published on 23 Feb 2026 - 6:39

score 107 · Answer 12 · 2018-09-01 04:30:38

107

Views

Prove that if: $g: \omega_1\rightarrow\omega_1$ then for some $\alpha<\omega_1$: $\forall \beta<\alpha: g(\beta)<\alpha$

Published on 01 Sep 2018 - 4:30

score 140 · Answer 13 · 2018-09-03 07:30:46

140

Views

If $\omega^\alpha$ has cofinality $\omega^\beta$, and $\beta\le\gamma\le\alpha$, does it also have a cofinal subset of order type $\omega^\gamma$?

Published on 03 Sep 2018 - 7:30

score 198 · Answer 14 · 2018-09-03 08:08:37

198

Views

Given an ordinal with a particular cofinality, can we find other cofinal subsets with order type and cofinality at least that large?

Published on 03 Sep 2018 - 8:08

score 538 · Answer 15 · 2026-03-22 17:18:43

538

Views

Is it possible to construct a model of oracle Turing machines that correspond to $\omega_n^\text{CK}$, where $n$ is greater than $1$?

Published on 22 Mar 2026 - 17:18

List Question

Should I write these ordinal operations in Cantor normal form?

Show that $A$ or $B$ must be bounded in $\omega_1$

How should I write this function $f:\mathcal P_{fin}(\omega^{<\omega})\to \mathcal P_{fin}(\omega^{<\omega})$?

Ordinals in category theory?

Proving the Bourbaki–Witt Theorem using Recursion.

What is the order type of the set of smooth functions ordered by growth rate?

When does an injective function $\omega^{<\omega}\to\Bbb N$ have positive density in the integers?

Finding a well-ordering of the natural numbers of a given order type

How to formally use transfinite recursion to construct a sequence for a proof of Zorn's lemma

Is it possible to construct order types using sets?

$\omega_1$ is a limit point of the subset $[0,\omega_1)$

Prove that if: $g: \omega_1\rightarrow\omega_1$ then for some $\alpha<\omega_1$: $\forall \beta<\alpha: g(\beta)<\alpha$

If $\omega^\alpha$ has cofinality $\omega^\beta$, and $\beta\le\gamma\le\alpha$, does it also have a cofinal subset of order type $\omega^\gamma$?

Given an ordinal with a particular cofinality, can we find other cofinal subsets with order type and cofinality at least that large?

Is it possible to construct a model of oracle Turing machines that correspond to $\omega_n^\text{CK}$, where $n$ is greater than $1$?

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