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Sep
13
revised Is a $0$-hyperbolic group free?
added 235 characters in body
Sep
10
revised $R$ is not a direct Sum of its subgroups
added 2 characters in body; edited tags; edited title
Sep
10
comment $R$ is not a direct Sum of its subgroups
Where is the problem? I don't understand your argument.
Sep
10
answered $R$ is not a direct Sum of its subgroups
Sep
2
comment $\mathbb S_n$ as semidirect product
The OP did not seem to know how to start, and the sequence precisely suggests to take a morphism $f : \mathbb{Z}_2 \to S_n$ so that $\mathrm{sign} \circ f = \mathrm{Id}$, and define $\rho : x \mapsto (y \mapsto f(x)yf(x)^{-1})$. But it's my opinion.
Sep
2
answered $\mathbb S_n$ as semidirect product
Aug
30
revised Infinite geodesic rays leaving a K-quasiconvex subgroup stay K-close to it.
added 11 characters in body
Aug
30
comment $\mathrm{Homeo}_{\mathbb{Z}} (\mathbb{R})$ is a perfect group
I come back to your answer, with a little more background, and the proof you sketch seems to be very nice! Do you have some precise references? (I searched on Ghys' webpage, but there are a lot of things.)
Aug
25
comment Show $C^\prime $ is a subgroup of $G$
Notice that the equality is equivalent to $(x^{-1}a)^2=(ax^{-1})^2$ and apply the same argument as above.
Aug
24
answered Show $C^\prime $ is a subgroup of $G$
Aug
19
comment What does $GL_n(R)$ look like?
A related question: math.stackexchange.com/questions/692862/…
Aug
16
comment How to prove $\det(e^A) = e^{\operatorname{tr}(A)}$?
The result is known as Jacobi's formula: en.wikipedia.org/wiki/Jacobi's_formula
Aug
5
comment If $H$ is a subgroup of $G$, then the inclusion is a quasi-isometry if and only if $H$ has finite index in $G$.
Are all your groups finitely-generated?
Aug
4
answered Is a $0$-hyperbolic group free?
Aug
4
comment Examples of “Non-Logical Theorems” Proven by Logic
@KyleGannon: Some examples are given there math.stackexchange.com/questions/282144/…
Aug
2
asked Why does the sign $\times$ vanish in mathematical expressions?
Aug
2
comment Is a $0$-hyperbolic group free?
In fact, it was not $1$ but $\mathrm{l}$. It is clearer if I write $\ell$, sorry.
Aug
2
revised Is a $0$-hyperbolic group free?
deleted 12 characters in body
Aug
1
revised Is a $0$-hyperbolic group free?
edited body
Aug
1
answered Infinite geodesic rays leaving a K-quasiconvex subgroup stay K-close to it.