Timeline for Are there quasiconvex normal subgroups?
Current License: CC BY-SA 3.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jan 8, 2015 at 1:59 | comment | added | Igor Rivin | @YCor of course, but I am just curious whether Greenberg's proof is actually different... | |
| Jan 7, 2015 at 23:51 | comment | added | YCor | @Igor: often a particular case of a theorem is harder (say, more tricky) than the general case, because the general statement better isolates the possible ways to find the proof. | |
| Jan 7, 2015 at 16:20 | comment | added | HJRW | Of course. But he did it before hyperbolic groups had been invented, and probably phrased his proof differently. I haven't looked at his paper. | |
| Jan 7, 2015 at 16:13 | comment | added | Igor Rivin | But isn't the proof the same in that case? | |
| Jan 7, 2015 at 16:02 | comment | added | HJRW | @Igor, he did Fuchsian groups. | |
| Jan 7, 2015 at 14:54 | comment | added | Igor Rivin | What did Greenberg do? | |
| Jan 7, 2015 at 14:14 | comment | added | YCor | The proof can be included: if $H$ is quasi-convex of infinite index, then $\partial H$ is a proper closed subset of $\partial G$, and $H$ normal implies that it's $G$-invariant. Since $G$ (which can be supposed non-elementary) is minimal on $\partial G$, this implies $\partial H=\emptyset$, hence $H$ is finite. | |
| Jan 7, 2015 at 13:51 | vote | accept | Pablo | ||
| Jan 7, 2015 at 13:31 | history | answered | HJRW | CC BY-SA 3.0 |