Question

What is the exact reason why the class of all ordinals, $\textbf{ORD}$ is not a set?

score 1k · Answer 1 · 2019-11-07 05:14:27

1k

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What is the exact reason why the class of all ordinals, $\textbf{ORD}$ is not a set?

Published on 07 Nov 2019 - 5:14

score 135 · Answer 2 · 2019-11-07 11:42:07

135

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Question Involving Strength of Fodor's Lemma, No CH Assumption

Published on 07 Nov 2019 - 11:42

score 231 · Answer 3 · 2026-03-27 04:22:03

231

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What is the highest ordinal that can’t be obtained from Kleene’s O with oracles?

Published on 27 Mar 2026 - 4:22

score 151 · Answer 4 · 2026-03-27 08:26:44

151

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Is there a simple oracle that computes the ordinal $\beta_0$?

Published on 27 Mar 2026 - 8:26

score 186 · Answer 5 · 2026-03-26 21:56:10

186

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What is the smallest ordinal not computable by using artihmetical truth as an oracle?

Published on 26 Mar 2026 - 21:56

score 328 · Answer 6 · 2019-11-09 06:47:43

328

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Why does the Well Ordering Theorem imply decreasing ordinals go to zero?

Published on 09 Nov 2019 - 6:47

score 98 · Answer 7 · 2026-03-25 01:29:20

98

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At which ordinal this "counting" ordinal language would fail?

Published on 25 Mar 2026 - 1:29

score 322 · Answer 8 · 2026-03-26 19:24:17

322

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What ordinals are computable using $\Sigma^1_2$ and $\Pi^1_2$ truth?

Published on 26 Mar 2026 - 19:24

score 127 · Answer 9 · 2019-11-14 03:23:17

127

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How far can an ordinal hierarchy of recursive functions go?

Published on 14 Nov 2019 - 3:23

score 80 · Answer 10 · 2019-11-15 21:38:17

80

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Can one define the $\omega$th term of a geometric sequence?

Published on 15 Nov 2019 - 21:38

score 121 · Answer 11 · 2019-11-20 18:34:15

121

Views

Prove If $\alpha$ is a non zero limit ordinal then ${\omega}^{\alpha}$ is a limit ordinal

Published on 20 Nov 2019 - 18:34

score 332 · Answer 12 · 2026-03-26 06:21:21

332

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Hessenberg power of ordinals

Published on 26 Mar 2026 - 6:21

score 1.9k · Answer 13 · 2026-03-26 06:20:15

1.9k

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How to prove a set is well-ordered

Published on 26 Mar 2026 - 6:20

score 76 · Answer 14 · 2026-03-25 12:46:20

76

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Is a continuous net of hyperreal numbers eventually constant?

Published on 25 Mar 2026 - 12:46

score 101 · Answer 15 · 2019-11-29 18:56:24

101

Views

Pigeonhole principle for ordinal numbers

Published on 29 Nov 2019 - 18:56

List Question

What is the exact reason why the class of all ordinals, $\textbf{ORD}$ is not a set?

Question Involving Strength of Fodor's Lemma, No CH Assumption

What is the highest ordinal that can’t be obtained from Kleene’s O with oracles?

Is there a simple oracle that computes the ordinal $\beta_0$?

What is the smallest ordinal not computable by using artihmetical truth as an oracle?

Why does the Well Ordering Theorem imply decreasing ordinals go to zero?

At which ordinal this "counting" ordinal language would fail?

What ordinals are computable using $\Sigma^1_2$ and $\Pi^1_2$ truth?

How far can an ordinal hierarchy of recursive functions go?

Can one define the $\omega$th term of a geometric sequence?

Prove If $\alpha$ is a non zero limit ordinal then ${\omega}^{\alpha}$ is a limit ordinal

Hessenberg power of ordinals

How to prove a set is well-ordered

Is a continuous net of hyperreal numbers eventually constant?

Pigeonhole principle for ordinal numbers

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