Nielsen-Schreier theorem
Every subgroup
(http://planetmath.org/Subgroup) of a free group
is free.
This theorem is named after Jakob Nielsen, who in 1921 proved that every subgroup of a free group of finite rank (http://planetmath.org/FreeGroup) is free, and Otto Schreier, who proved the full result in 1927.
| Title | Nielsen-Schreier theorem |
|---|---|
| Canonical name | NielsenSchreierTheorem |
| Date of creation | 2013-03-22 12:54:07 |
| Last modified on | 2013-03-22 12:54:07 |
| Owner | yark (2760) |
| Last modified by | yark (2760) |
| Numerical id | 9 |
| Author | yark (2760) |
| Entry type | Theorem |
| Classification | msc 20E05 |