Is the union of sigma algebras a sigma algebra?
19996
Example where union of increasing sigma algebras is not a sigma algebra
50880
Expressing $\Bbb N$ as an infinite union of disjoint infinite subsets.
146261
Difference between topology and sigma-algebra axioms.
52012
Is there exist a homemoorphism between either pair of $(0,1),(0,1],[0,1]$
60032
If the measure of union = sum of outer measures, then the sets are measurable
135548
Every section of a measurable set is measurable? (in the product sigma-algebra)
16048
Approximating a $\sigma$-algebra by a generating algebra
46775
If $\sigma_n=\frac{s_1+s_2+\cdots+s_n}{n}$ then $\operatorname{{lim sup}}\sigma_n \leq \operatorname{lim sup} s_n$
29637
$\sigma$-algebra of sets that are both $G_\delta$ and $F_\sigma$
58484
Is the topological product $\Pi \{G_\alpha: \alpha < \kappa\} $ a topological group?
10247
What is the minimum $ \sigma$-algebra that contains open intervals with rational endpoints
117185
The union of a strictly increasing sequence of $\sigma$-algebras is not a $\sigma$-algebra
150704
Do the ladder operators $a$ and $a^\dagger$ form a complete algebra basis?
950
Doubts on the axiom of union?
151559
Please help: How to show that Aut(G) is a subgroup of Sym(G)
80735
Show that $C_0([a, b], \mathbb{R})$ is not $\sigma$-compact
16892
Reference request: product Borel $\sigma$-algebra of non-separable metric spaces