$\mathbb{Q}$ is in the Borel $\sigma$-algebra
125894
Prove that $\mathbb{Q}$ belongs to the Borel $\sigma$-algebra of $\mathbb{R}$
36131
$\sigma$-algebra vs. $\sigma$-field: is there any difference?
124230
What is $\operatorname{Hom}_\mathbb{Z}(\mathbb{Q}/\mathbb{Z},\mathbb{Q}/\mathbb{Z})$?
57166
Showing that $\Bbb R[x] / \langle x^2 + 1 \rangle$ is isomorphic to $\Bbb C$ question
134840
Generators and relations for $\text{PSL}(2, \mathbb{F}_q)$
44259
Heine-Borel Theorem ($\mathbb{R}^k$) (in ZF)
61103
Prove that $\mathbb{|Q| = |Q\times Q|}$
76501
How can we show that $\mathbb Q$ is not a free $\mathbb Z$-module?
134983
Borel sigma algebra not containing all subsets of $\mathbb{R}$?
83830
Sigma algebra generated by the set of all singletons
104308
Proving a set is a Sigma Algebra
94579
$\mathbb{Q}[x,y]/\langle x^2+y^2-1 \rangle$ is an integral domain, and its field of fractions is isomorphic to $\mathbb Q(t)$
65098
Number of $\sigma$  -Algebra on the finite set
53432
What is the algebraic closure of $\mathbb F_q$?
153542
Fixed Field of $\sigma, \tau$
147783
Showing a sigma algebra is the union of certain collection of sigma algebras
117185
The union of a strictly increasing sequence of $\sigma$-algebras is not a $\sigma$-algebra