Question

Should I write these ordinal operations in Cantor normal form?

score 170 · Answer 1 · 2026-04-14 04:05:45

170

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Should I write these ordinal operations in Cantor normal form?

Published on 14 Apr 2026 - 4:05

score 73 · Answer 2 · 2026-04-12 02:07:04

73

Views

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

Published on 12 Apr 2026 - 2:07

score 125 · Answer 3 · 2026-04-10 14:43:16

125

Views

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

Published on 10 Apr 2026 - 14:43

score 783 · Answer 4 · 2026-04-14 20:59:16

783

Views

Ordinals in category theory?

Published on 14 Apr 2026 - 20:59

score 368 · Answer 5 · 2026-04-14 00:39:17

368

Views

Proving the Bourbaki–Witt Theorem using Recursion.

Published on 14 Apr 2026 - 0:39

score 121 · Answer 6 · 2026-05-10 16:14:40

121

Views

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

Published on 10 May 2026 - 16:14

score 93 · Answer 7 · 2026-04-15 13:14:21

93

Views

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

Published on 15 Apr 2026 - 13:14

score 612 · Answer 8 · 2026-04-20 02:39:07

612

Views

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

Published on 20 Apr 2026 - 2:39

score 1k · Answer 9 · 2026-04-20 11:54:00

1k

Views

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

Published on 20 Apr 2026 - 11:54

score 67 · Answer 10 · 2026-03-25 14:19:26

67

Views

Is it possible to construct order types using sets?

Published on 25 Mar 2026 - 14:19

score 162 · Answer 11 · 2026-05-04 02:26:19

162

Views

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

Published on 04 May 2026 - 2:26

score 110 · Answer 12 · 2026-04-13 18:16:13

110

Views

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

Published on 13 Apr 2026 - 18:16

score 144 · Answer 13 · 2026-05-10 15:03:30

144

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 10 May 2026 - 15:03

score 202 · Answer 14 · 2026-05-10 13:50:28

202

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 10 May 2026 - 13:50

score 546 · Answer 15 · 2026-05-10 15:58:48

546

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 10 May 2026 - 15:58

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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