Question

Is Halmos' use of the Axiom of Substitution wrong in Ch. 19 Naive Set Theory?

score 240 · Answer 1 · 2019-02-12 02:10:30

240

Views

Is Halmos' use of the Axiom of Substitution wrong in Ch. 19 Naive Set Theory?

Published on 12 Feb 2019 - 2:10

score 543 · Answer 2 · 2026-03-25 13:33:19

543

Views

Fixed points of ordinal exponentiation for bases besides $\omega$

Published on 25 Mar 2026 - 13:33

score 267 · Answer 3 · 2026-03-25 13:42:07

267

Views

Different definition of Veblen functions

Published on 25 Mar 2026 - 13:42

score 79 · Answer 4 · 2019-02-15 10:27:02

79

Views

How to justify the uniqueness and existence of this sequence by Transfinite Recursion Theorem?

Published on 15 Feb 2019 - 10:27

score 53 · Answer 5 · 2019-02-17 01:40:50

53

Views

Solution verification: Writing a sum in the Cantor normal form

Published on 17 Feb 2019 - 1:40

score 56 · Answer 6 · 2019-02-19 23:59:21

56

Views

Set of well-orderings of a given ordinal

Published on 19 Feb 2019 - 23:59

score 86 · Answer 7 · 2026-03-25 17:26:54

86

Views

What rule allows to determine the symbol on an $i$-th cell of the tape of an Infinite Time Turing Machine at any limit stage?

Published on 25 Mar 2026 - 17:26

score 354 · Answer 8 · 2019-02-20 22:15:07

354

Views

A particular class which satisfies all ZF axioms except for the axiom of infinity

Published on 20 Feb 2019 - 22:15

score 122 · Answer 9 · 2019-02-27 03:13:35

122

Views

What is $\sup \emptyset$ (if exists) w.r.t the usual ordering on ordinals?

Published on 27 Feb 2019 - 3:13

score 165 · Answer 10 · 2026-03-25 01:27:25

165

Views

Modifying the "base" of Veblen's hierarchy to exceed $\Gamma_0$

Published on 25 Mar 2026 - 1:27

score 44 · Answer 11 · 2019-03-01 18:50:13

44

Views

Unknown notation/omega

Published on 01 Mar 2019 - 18:50

score 55 · Answer 12 · 2026-03-25 20:14:12

55

Views

Can $\kappa$-club is defined for any class of ordinals?

Published on 25 Mar 2026 - 20:14

score 113 · Answer 13 · 2026-03-25 01:31:14

113

Views

Does there exist a notion of "growth rate", big-O notation, etc for ordinal (normal) functions?

Published on 25 Mar 2026 - 1:31

score 227 · Answer 14 · 2019-03-05 07:38:04

227

Views

Proving (without AC) that there is a surjective function from $\mathcal{P}(\omega)$ to $\omega_1$.

Published on 05 Mar 2019 - 7:38

score 476 · Answer 15 · 2019-03-06 07:16:59

476

Views

What sets are there with order type $\omega^2$

Published on 06 Mar 2019 - 7:16

List Question

Is Halmos' use of the Axiom of Substitution wrong in Ch. 19 Naive Set Theory?

Fixed points of ordinal exponentiation for bases besides $\omega$

Different definition of Veblen functions

How to justify the uniqueness and existence of this sequence by Transfinite Recursion Theorem?

Solution verification: Writing a sum in the Cantor normal form

Set of well-orderings of a given ordinal

What rule allows to determine the symbol on an $i$-th cell of the tape of an Infinite Time Turing Machine at any limit stage?

A particular class which satisfies all ZF axioms except for the axiom of infinity

What is $\sup \emptyset$ (if exists) w.r.t the usual ordering on ordinals?

Modifying the "base" of Veblen's hierarchy to exceed $\Gamma_0$

Unknown notation/omega

Can $\kappa$-club is defined for any class of ordinals?

Does there exist a notion of "growth rate", big-O notation, etc for ordinal (normal) functions?

Proving (without AC) that there is a surjective function from $\mathcal{P}(\omega)$ to $\omega_1$.

What sets are there with order type $\omega^2$

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