List questions from cardinals | MathQA

If $\mu$ is an infinite cardinal, there is a function $f:\mu\longrightarrow\mu$ such that $f^{-1}[\alpha]$ is cofinal in $\mu$ for all $\alpha\in\mu$.

Published on 22 Feb 2020 - 8:19

Inaccessible cardinal in a transitive model

Published on 28 Mar 2026 - 17:38

Collapsing cardinal $\lambda$ to $\omega$ by Cohen foricng

Published on 26 Mar 2026 - 6:09

Cardinality of prime numbers

Published on 28 Mar 2026 - 0:48

Let $A, B, X, Y$ be sets with $X \preccurlyeq A$ and $Y \preccurlyeq B$. Prove that, apart from exceptional case(s), $X^Y \preccurlyeq A^B$.

Published on 27 Feb 2020 - 14:07

Cofinality of a cardinal

Published on 28 Feb 2020 - 11:59

Cardinality of the star-product and cardinality of union

Published on 28 Feb 2020 - 13:04

Prove that the set $A$ of algebraic numbers is denumerable.

Published on 04 Mar 2020 - 1:19

Why $\aleph_0$ and $c$ are unequal transfinite cardinals?

Published on 06 Mar 2020 - 23:12

Confused about union while handling cardinal exponentiation

Published on 28 Mar 2026 - 0:36

Are there more rectangles than squares?

Published on 09 Mar 2020 - 3:11

Question about the cardinality

Published on 09 Mar 2020 - 4:22

What is the cardinality of the union of uncountable sets

Published on 09 Mar 2020 - 6:11

Cardinals comparison in Jones' lemma

Published on 25 Mar 2026 - 23:36

Do finite unions preserve cardinality?

Published on 14 Mar 2020 - 12:38