Subgroups of $\mathbb{R}/\mathbb{Z}$ are either cyclic or dense
67919
Subgroup of the unit circle under complex multiplication
111375
Normality of subgroups and Sylow groups under homomorphisms...
144258
How to show a group is cyclic?
112131
Characterizing all ring homomorphisms $C[0,1]\to\mathbb{R}$.
108305
How can we show that the dyadic rationals are dense in $\mathbb R$?
129485
A subgroup of a cyclic group is cyclic - Understanding Proof
95294
Dense subset of $C[0,1]$ which preserves rationals
30753
Showing there is no ring whose additive group is isomorphic to $\mathbb{Q}/\mathbb{Z}$
45727
If $G$ contains a normal subgroup $H \cong \mathbb{Z_2}$ such that $G/H$ is infinite cyclic, then $G \cong \mathbb{Z} \times \mathbb{Z_2}$
146028
$GL(n, \mathbb{C})$ is isomorphic to a subgroup of $GL(2n, \mathbb{R})$
50412
Prime elements in $\mathbb{Z}/n\mathbb{Z}$
3317
Subgroup generated by $2$ and $7$ in $(\mathbb Z,+)$
9232
Group with proper subgroups infinite cyclic
132386
Show that $(\mathbb{Q}^*,\cdot)$ and $(\mathbb{R}^*,\cdot)$ aren't cyclic
82843
Subgroups of $\Bbb{R}^n$ that are closed and discrete
39938
Subgroups of a cyclic group and their order.
37904
Prove that the multiplicative groups $\mathbb{R} - \{0\}$ and $\mathbb{C} - \{0\}$ are not isomorphic.