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 |