Why is an algebra not a $\sigma$-algebra by induction?
51877
Why is this 'Proof' by induction not valid?
63860
Measure of Dependence Between Two $\sigma$-algebras
134983
Borel sigma algebra not containing all subsets of $\mathbb{R}$?
50656
Intuition behind $k$-algebra, $k$-algebra morphisms?
20789
If $\Sigma \vdash \varphi$ then $\Sigma \vdash \forall x \varphi$. Why when $(\varphi \implies \forall x \varphi)$ is not true?
77507
Induction without a base case
66546
Tensor product of reduced $k$-algebras must be reduced?
16048
Approximating a $\sigma$-algebra by a generating algebra
80735
Show that $C_0([a, b], \mathbb{R})$ is not $\sigma$-compact
55148
Why is this isomorphism $M \otimes_K L \stackrel{\simeq}{\longrightarrow} M^{[L:K]}$ an isomorphism of $M$ - algebras?
147659
Counterexample to "if $f:A\to A$ induces the identity $\hat f:\operatorname{Spec}(A)\to\operatorname{Spec}(A)$, then $f=\operatorname{id}_A$"
38946
Show that $\{\cup_{n\in K} (n, n+1]: K \subset \mathbb{Z}\}$ is a $\sigma$-algebra on $\mathbb{R}$
47937
Example of a Borel set that is neither $F_\sigma$ nor $G_\delta$
17378
Characterize finite dimensional algebras without nilpotent elements
88099
Not $\sigma$-compact set without axiom of choice
3296
Proof That $\mathbb{R} \setminus \mathbb{Q}$ Is Not an $F_{\sigma}$ Set
146261
Difference between topology and sigma-algebra axioms.