List questions from ordinals | MathQA

Easier proof of homeomorphism classes of ordinals

Published on 13 Jan 2023 - 5:30

If $\omega\underline{\in}\alpha$ and $\alpha^2\underline{\in}\beta$ then $\alpha+\beta=\beta$

Published on 14 Jan 2023 - 13:58

How to calculate multiplication of transfinite nimbers with a Cantor normal form

Published on 26 Mar 2026 - 17:32

Definition of the ordinal rank of sentences of the natural number structure.

Published on 01 Apr 2026 - 14:24

Barwise exercise: nonprojectibles are recursively Mahlo

Published on 22 Jan 2023 - 4:51

$(\kappa \times 2,<_{lex}) \cong (\kappa,\in )$ for cardinal numbes $\kappa$.

Published on 24 Jan 2023 - 18:14

How large is the supremum of all countable ordinals that have absolute definitions?

Published on 26 Jan 2023 - 5:01