New posts in cardinals

How many ultrafilters there are in an infinite space?

general-topology proof-explanation cardinals filters

Cardinality and infinite sets: naturals, integers, rationals, bijections

elementary-set-theory cardinals

An easy to understand definition of $\omega_1$?

general-topology elementary-set-theory cardinals ordinals

Does well-ordering of the proper class of cardinal numbers imply choice?

set-theory cardinals axiom-of-choice

How do you prove the trichotomy law for cardinal numbers?

elementary-set-theory cardinals

In ZF, does there exist an ordinal of provably uncountable cofinality?

reference-request set-theory cardinals model-theory axiom-of-choice

Which ordinals can be "mistaken for" $\aleph_1$?

set-theory model-theory cardinals ordinals forcing

$ (1*...*1)(n) =\# \{(m_1,...,m_k)\in (\mathbb{N}\setminus \{0\})^k : m_1...m_k = n\} $

cardinals arithmetic-functions

Is the axiom of choice needed to show that $a^2=a$?

set-theory cardinals axiom-of-choice

Why was $\aleph$ (aleph) chosen for infinities?

elementary-set-theory notation math-history cardinals infinity

Bijection between $3^{\mathbb N}$ and $\mathcal P(\mathbb N)$?

functions elementary-set-theory cardinals multisets

What is the cardinality of a set of all monotonic functions on a segment $[0,1]$?

real-analysis cardinals

Cofinality of cardinals

elementary-set-theory cardinals

What's "the catch" in this question?

set-theory cardinals

Which set is greater in cardinality?

elementary-set-theory cardinals

Uncountably many functions coinciding only finitely many values

set-theory cardinals

Existence of a sequence that has every element of $\mathbb N$ infinite number of times

sequences-and-series cardinals natural-numbers

A bogus proof of countable power set [duplicate]

elementary-set-theory proof-verification cardinals

Wimpy powerset function

set-theory cardinals

Is the cardinality of uncountable $G_{\delta}$ set of $\mathbb{R}$ equals the cardinality of the continuum?

cardinals descriptive-set-theory