What is wrong with this proof there is no $\omega$-th worldly cardinal
38221
What is wrong with this proof there is no $\omega$-th worldly cardinal
135606
No function $f:\mathbb{Z}\rightarrow \{1, 2, 3\}$ satisfying $f(x)\ne f(y)$ for all integers $x,y$ and $|x-y|\in\{2, 3, 5\}$
153935
A weaker Axiom of Infinity?
65768
What is the cardinality of the set of the empty set?
45218
Comparing the two cardinals $\aleph_0^{\aleph_0}$ and $2^{\aleph_0}$
49155
$f: \Omega \rightarrow \Omega$ holomorphic, $f(0) = 0$, $f'(0) = 1$ implies $f(z) = z$
97156
ZFC + $\exists$ Standard model $\rightarrow$ Con(ZFC + $\exists \omega$-model)
27899
Can we prove the existence of $A\cup B$ without the union axiom?
86154
Why is this true? A set is Dedekind infinite if and only if equipotent to the union with the set containing itself
74734
(Enderton set theory) Hartog's theorem and cardinal numbers
21881
Prove that $\forall\alpha\geq\omega$, $|L_\alpha|=|\alpha|$ without AC
6427
how many infinite cardinals are smaller than $\aleph$?
67279
Is the union of finitely many open sets in an omega-cover contained within some member of the cover?
92639
Prove that the family of open sets in $\mathbb{R}$ has cardinality equal to $2^{\aleph_0}$
95240
Show that $({\mathbb{Q}},+)$ is not finitely generated using the Fundamental Theorem of Finitely Generated Abelian Groups.
16172
My proof of $I \otimes N \cong IN$ is clearly wrong, but where have I gone wrong?
132701
Contradicting Fubini's theorem