Proving Two Groups are not Isomorphic
88645
Prove that the additive groups $\mathbb{R}$ and $\mathbb{Q}$ are not isomorphic.
1686
Show that quotient rings are not isomorphic
152603
Group isomorphic to its automorphism group
81892
Find four groups of order 20 not isomorphic to each other.
146969
Proving that every group of order $4$ is isomorphic to $\Bbb Z_4$ or $\Bbb Z^*_8$
61373
A normal subgroup that is not a characteristic
933
How many groups exist with order $n$ (two isomorphic groups are treated as the same group)
150207
Non isomorphic subgroups of cyclic groups
3462
Proving a set of automorphisms of a group is a group under composition
67374
Is it true that $\mathbb{R}$ and $\mathbb{R}^2$ are isomorphic as abelian groups?
146356
To prove two sets are isomorphic is it sufficient to find 2 injections or 2 surjections?
135241
Show that $\mathbb{Z}/n^2\mathbb{Z}$ is not isomorphic to other group
23279
Group Theory Isomorphism
115649
Proving two sets $A, B$ are order isomorphic
46260
Prove that a group generated by two elements of order $2$, $x$ and $y$, is isomorphic to $D_{2n}$, where $n = |xy|.$
65968
Prove that any two cyclic groups of the same order are isomorphic?
81238
Is $O(2)$ really not isomorphic to $SO(2)\times \{-1,1\}$?