Question

Can you lay $ \aleph_1$ many people on a railway track?

score 483 · Answer 1 · 2026-04-13 17:28:05

483

Views

Can you lay $ \aleph_1$ many people on a railway track?

Published on 13 Apr 2026 - 17:28

score 592 · Answer 2 · 2026-05-10 14:50:23

592

Views

Ordinal vs cardinal dimension

Published on 10 May 2026 - 14:50

score 108 · Answer 3 · 2026-04-29 12:55:22

108

Views

Modifying a sequence of ordinals to be increasing and continuous. (To find names of small rank.)

Published on 29 Apr 2026 - 12:55

score 131 · Answer 4 · 2026-04-13 23:37:37

131

Views

When does $\omega \cdot \alpha = \alpha$?

Published on 13 Apr 2026 - 23:37

score 95 · Answer 5 · 2026-04-13 19:30:15

95

Views

Given a Baire one function, is it true that its restriction to special subset continuous?

Published on 13 Apr 2026 - 19:30

score 267 · Answer 6 · 2026-04-08 20:16:52

267

Views

How can I show $\omega + \omega^2 = \omega^2$, regarding $\omega$ as an ordinal?

Published on 08 Apr 2026 - 20:16

score 235 · Answer 7 · 2026-05-10 12:34:44

235

Views

Find a subset of $(\mathbb{Q}, <)$ isomorphic to $Exp(\omega, \omega)$ as well ordered set

Published on 10 May 2026 - 12:34

score 57 · Answer 8 · 2026-04-14 14:35:32

57

Views

Interchanging supremums in ordinal arithmetic

Published on 14 Apr 2026 - 14:35

score 87 · Answer 9 · 2026-04-17 18:08:16

87

Views

For ordinal $\alpha > 1$, what's the smallest $\beta > 0$ such that $\alpha \beta = \beta$?

Published on 17 Apr 2026 - 18:08

score 51 · Answer 10 · 2026-04-12 16:20:26

51

Views

could be this a general (and useful) rule to operate with ordinal?

Published on 12 Apr 2026 - 16:20

score 103 · Answer 11 · 2026-04-10 19:56:59

103

Views

something more about $\omega ^ \omega$

Published on 10 Apr 2026 - 19:56

score 299 · Answer 12 · 2026-04-14 03:46:11

In ZFC if there is a bijection between any set and some ordinal, why use others sets in the first place? Why not assume everything is an ordinal?

score 328 · Answer 13 · 2026-04-14 15:36:16

328

Views

Cofinality of a limit ordinal is equal to the cofinality of a given normal operation - Proof

Published on 14 Apr 2026 - 15:36

score 65 · Answer 14 · 2026-04-15 07:39:30

65

Views

Clubs and some fixed type is realized by uncountably many elements.

Published on 15 Apr 2026 - 7:39

score 81 · Answer 15 · 2026-04-12 03:58:37

81

Views

Trouble understanding a property of ordinals

Published on 12 Apr 2026 - 3:58

List Question

Can you lay $ \aleph_1$ many people on a railway track?

Ordinal vs cardinal dimension

Modifying a sequence of ordinals to be increasing and continuous. (To find names of small rank.)

When does $\omega \cdot \alpha = \alpha$?

Given a Baire one function, is it true that its restriction to special subset continuous?

How can I show $\omega + \omega^2 = \omega^2$, regarding $\omega$ as an ordinal?

Find a subset of $(\mathbb{Q}, <)$ isomorphic to $Exp(\omega, \omega)$ as well ordered set

Interchanging supremums in ordinal arithmetic

For ordinal $\alpha > 1$, what's the smallest $\beta > 0$ such that $\alpha \beta = \beta$?

could be this a general (and useful) rule to operate with ordinal?

something more about $\omega ^ \omega$

In ZFC if there is a bijection between any set and some ordinal, why use others sets in the first place? Why not assume everything is an ordinal?

Cofinality of a limit ordinal is equal to the cofinality of a given normal operation - Proof

Clubs and some fixed type is realized by uncountably many elements.

Trouble understanding a property of ordinals

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