Question

Definable well-ordered class relations

score 127 · Answer 1 · 2026-03-28 04:32:56

127

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Definable well-ordered class relations

Published on 28 Mar 2026 - 4:32

score 242 · Answer 2 · 2021-03-25 15:56:46

242

Views

Why is an unbounded subset of $\omega_1$ uncountable?

Published on 25 Mar 2021 - 15:56

score 169 · Answer 3 · 2026-03-28 04:33:27

169

Views

Constructing a Abelian group from a von Neumann ordinal

Published on 28 Mar 2026 - 4:33

score 227 · Answer 4 · 2026-03-26 16:06:52

227

Views

Is there a generalization of transfinite recursion that allows defining proper classes?

Published on 26 Mar 2026 - 16:06

score 49 · Answer 5 · 2021-04-10 11:19:10

Two non-decreasing sequences $a,b : \alpha \to \alpha$ such that $a$ is a subsequence of $b$ and vice versa, but they are not the same sequence.

score 58 · Answer 6 · 2021-04-13 13:07:22

58

Views

Refinement of an infinite chain

Published on 13 Apr 2021 - 13:07

score 150 · Answer 7 · 2021-04-13 22:49:37

150

Views

Defining Long Line like $\mathbb R \times [0,1)$ (cartesian product of real line with unit interval) instead of using ordinals?

Published on 13 Apr 2021 - 22:49

score 124 · Answer 8 · 2026-03-29 03:45:12

124

Views

Can an axiomatic system have uncountably many axioms?

Published on 29 Mar 2026 - 3:45

score 327 · Answer 9 · 2021-04-16 16:56:49

327

Views

Are all cardinals of the form $\aleph_0$ or $2^\alpha$?

Published on 16 Apr 2021 - 16:56

score 109 · Answer 10 · 2026-03-28 00:56:17

109

Views

Some observations about third-order functionals: any relationships between them?

Published on 28 Mar 2026 - 0:56

score 107 · Answer 11 · 2021-04-27 09:19:03

107

Views

Can we show for ordinal numbers that $\alpha\in\beta$ implies $\alpha\subsetneqq\beta$ without axiom of regularity?

Published on 27 Apr 2021 - 9:19

score 361 · Answer 12 · 2026-04-03 19:48:45

361

Views

König's Lemma in set theory, why is the finite branching needed?

Published on 03 Apr 2026 - 19:48

score 107 · Answer 13 · 2021-04-29 07:56:23

107

Views

Is there an ordinal number $x$ such that $\omega^\omega \cdot x=\omega_1$?

Published on 29 Apr 2021 - 7:56

score 147 · Answer 14 · 2021-04-29 10:03:45

147

Views

limit ordinal as a countable sequence

Published on 29 Apr 2021 - 10:03

score 91 · Answer 15 · 2026-03-31 12:14:29

91

Views

Is there any use to $\mathbb{N}$ as a sort of ring mod an infinite number?

Published on 31 Mar 2026 - 12:14

List Question

Definable well-ordered class relations

Why is an unbounded subset of $\omega_1$ uncountable?

Constructing a Abelian group from a von Neumann ordinal

Is there a generalization of transfinite recursion that allows defining proper classes?

Two non-decreasing sequences $a,b : \alpha \to \alpha$ such that $a$ is a subsequence of $b$ and vice versa, but they are not the same sequence.

Refinement of an infinite chain

Defining Long Line like $\mathbb R \times [0,1)$ (cartesian product of real line with unit interval) instead of using ordinals?

Can an axiomatic system have uncountably many axioms?

Are all cardinals of the form $\aleph_0$ or $2^\alpha$?

Some observations about third-order functionals: any relationships between them?

Can we show for ordinal numbers that $\alpha\in\beta$ implies $\alpha\subsetneqq\beta$ without axiom of regularity?

König's Lemma in set theory, why is the finite branching needed?

Is there an ordinal number $x$ such that $\omega^\omega \cdot x=\omega_1$?

limit ordinal as a countable sequence

Is there any use to $\mathbb{N}$ as a sort of ring mod an infinite number?

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