Are there $C^1$ groups that aren't smooth?
102246
Are there nonsmooth Lie groups?
33309
Subgroup of $\mathbb{R}$ either dense or has a least positive element?
52014
Showing $(C[0,1], d_1)$ is not a complete metric space
25421
Simple or not simple Groups
86542
Group of positive rationals under multiplication not isomorphic to group of rationals
80381
Groups with "few" subgroups
37841
Product of quotient maps and quotient space that is not Hausdorff
70298
Are quotients of chain groups $C_n(X)/C_n(A)$ still free?
80418
The "Easiest" non-smoothable manifold
33370
Show that the one point compactification of $\mathbb{Q}$ is not Hausdorff
84869
Are the groups $\mathbb{C}$ and $\mathbb{R}$ isomorphic?
26256
Characterizing Dense Subgroups of the Reals
61373
A normal subgroup that is not a characteristic
156679
$K[X,Y]/(XY-1)$ not isomorphic to $K[T]$
91021
Torsion elements of a group aren't necessarily a subgroup
70688
How can I prove that the additive group of rationals is not isomorphic to a direct product of two nontrivial groups?
57883
Example of a Subgroup That Is Not Normal