Question

A cofinal function into a limit ordinal

score 92 · Answer 1 · 2026-04-09 19:22:03

92

Views

A cofinal function into a limit ordinal

Published on 09 Apr 2026 - 19:22

score 54 · Answer 2 · 2026-04-09 07:01:53

54

Views

Understanding a proof about regular cardinals from "Set Theory for the Working Mathematician"

Published on 09 Apr 2026 - 7:01

score 204 · Answer 3 · 2026-04-08 21:05:44

204

Views

Does there exist a strict numeric measure of the strength for any set theory (relative to a corresponding proof-theoretic ordinal)?

Published on 08 Apr 2026 - 21:05

score 220 · Answer 4 · 2026-04-11 17:38:08

220

Views

Every countable linearly ordered set is similar to one of its subsets

Published on 11 Apr 2026 - 17:38

score 761 · Answer 5 · 2026-04-16 03:25:59

A proper subset of $\Bbb Q$ that is order-isomorphic to $\Bbb Q$; An infinite set that is NOT order-isomorphic to any of its proper subset

score 284 · Answer 6 · 2026-04-10 10:32:22

284

Views

Using the Definition of Dedekind-Infinite to Replace the Axiom of Infinity

Published on 10 Apr 2026 - 10:32

score 105 · Answer 7 · 2026-04-09 09:28:13

105

Views

Specific Question about $\omega_1$ hierarchies

Published on 09 Apr 2026 - 9:28

score 115 · Answer 8 · 2026-04-17 05:07:22

115

Views

Is there a good notion of hypercomputation which allows inaccessible-length computations?

Published on 17 Apr 2026 - 5:07

score 145 · Answer 9 · 2026-04-11 05:08:27

145

Views

Hypertask, Arithmetical hierarchy and beyond

Published on 11 Apr 2026 - 5:08

score 3.5k · Answer 10 · 2026-04-11 13:07:09

3.5k

Views

Proof of Zorn's Lemma

Published on 11 Apr 2026 - 13:07

score 204 · Answer 11 · 2026-04-13 17:27:06

204

Views

Can there be a proper class of $\alpha$-inaccessibles for any ordinal $\alpha$?

Published on 13 Apr 2026 - 17:27

score 150 · Answer 12 · 2026-04-14 18:43:20

150

Views

existence of a branch of length $\kappa$ in a tree of height $\kappa$ whose levels are finite

Published on 14 Apr 2026 - 18:43

score 79 · Answer 13 · 2026-04-14 22:35:22

79

Views

ZF + (Weak Axiom) $\vdash$ Dedekind Finite Implies Finite (Direct Proof)

Published on 14 Apr 2026 - 22:35

score 162 · Answer 14 · 2026-04-15 08:43:52

162

Views

$\kappa^+$ tree with no $\kappa^+$ branch

Published on 15 Apr 2026 - 8:43

score 99 · Answer 15 · 2026-04-14 17:49:32

99

Views

What axioms do we need to exhibit a disjoint set of same size?

Published on 14 Apr 2026 - 17:49

List Question

A cofinal function into a limit ordinal

Understanding a proof about regular cardinals from "Set Theory for the Working Mathematician"

Does there exist a strict numeric measure of the strength for any set theory (relative to a corresponding proof-theoretic ordinal)?

Every countable linearly ordered set is similar to one of its subsets

A proper subset of $\Bbb Q$ that is order-isomorphic to $\Bbb Q$; An infinite set that is NOT order-isomorphic to any of its proper subset

Using the Definition of Dedekind-Infinite to Replace the Axiom of Infinity

Specific Question about $\omega_1$ hierarchies

Is there a good notion of hypercomputation which allows inaccessible-length computations?

Hypertask, Arithmetical hierarchy and beyond

Proof of Zorn's Lemma

Can there be a proper class of $\alpha$-inaccessibles for any ordinal $\alpha$?

existence of a branch of length $\kappa$ in a tree of height $\kappa$ whose levels are finite

ZF + (Weak Axiom) $\vdash$ Dedekind Finite Implies Finite (Direct Proof)

$\kappa^+$ tree with no $\kappa^+$ branch

What axioms do we need to exhibit a disjoint set of same size?

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