I can construct a finitely presented group $G$ with the following property (which I use to construct something else). >Given a finitely preseted group $\Gamma$, there is a subgroup $G'\le G$ of finite index such that $$\Gamma=G'/\langle\mathrm{Tor}\, G'\rangle ,$$ where $\mathrm{Tor}\, G'\subset G'$ is the set of all elements of finite order. I think to call such group $G$ *universal*. **Questions:** - Was it already constructed? - Does it already has a name? Is there any closely related terminology? ---- **P.S.** - The group which I construct is in fact hyperbolic. - The construction is simple, but it takes 2--3 pages. Let me know if you see a short way to do it. - [Here][1], the term "universal group" was used in very similar context (thanks to D. Panov for the reference). - Thanks to all your comments, we call them ["telescopic" actions][2] now. [1]: http://www.springerlink.com/content/k332884x7m10l654/ [2]: http://front.math.ucdavis.edu/1104.4814