Timeline for Group extensions and actions on categories
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 20, 2012 at 16:54 | history | edited | Erwan Biland | CC BY-SA 3.0 |
edited body
|
| Feb 17, 2012 at 20:44 | answer | added | Ronnie Brown | timeline score: 1 | |
| Feb 15, 2012 at 18:46 | answer | added | Mkouboi | timeline score: 3 | |
| Feb 15, 2012 at 7:15 | comment | added | Thomas Nikolaus | @Finn: Of course you are right. BH is equivalent to H-Torsors. | |
| Feb 15, 2012 at 1:19 | vote | accept | Erwan Biland | ||
| Feb 14, 2012 at 22:40 | comment | added | Finn Lawler | (Also, I think H-Set is equivalent not to BH but to [BH, Set].) | |
| Feb 14, 2012 at 22:38 | comment | added | Finn Lawler | John Baez wrote about Schreier theory in his TWF series: math.ucr.edu/home/baez/week223.html -- he points out a good reference for the Schreier theory of groupoids too: arxiv.org/abs/math.CT/0410202 . | |
| Feb 14, 2012 at 22:20 | comment | added | Joël | Martin, are you are you read well the question ? This equivalence of category, if not utterly deep, is not to be found "in any introduction to semi-direct products", and is surely about category-theory. | |
| Feb 14, 2012 at 21:43 | comment | added | Thomas Nikolaus | The category of H-sets is equivalent to the category BH with one object and H as automorphisms. Then you statement goes by the name of Schreier-Theory or Dedecker-Cocycles and dates back to the beginning of the 20th century. | |
| Feb 14, 2012 at 21:32 | comment | added | Martin Brandenburg | I think this question is too localized for MO. It is a basic result which is contained in every introduction to semidirect products of groups. I think that the category-theory tag is wrong. | |
| Feb 14, 2012 at 21:32 | answer | added | Evan Jenkins | timeline score: 9 | |
| Feb 14, 2012 at 21:30 | history | edited | Yemon Choi |
added ref-request tag
|
|
| Feb 14, 2012 at 21:15 | history | asked | Erwan Biland | CC BY-SA 3.0 |