We give a simple proof of the finite presentation of Sela's limit groupsby using free actions on $\bbR^n$-trees.We first prove that Sela's limit groups do have a free action on an $\bbR^n$-tree.We then prove that a finitely generated group having a free action on an $\bbR^n$-tree can be obtained from free abelian groups and surface groups by a finite sequence of free products and amalgamations over cyclic groups.As a corollary, such a group is finitely presented, has a finite classifying space,its abelian subgroups are finitely generated and contains onlyfinitely many conjugacy classes of non-cyclic maximal abelian subgroups.
@article{hal-00000428,
author = {Guirardel, Vincent},
title = {Limit groups and groups acting freely on R^n-trees.},
journal = {HAL},
volume = {2004},
number = {0},
year = {2004},
language = {en},
url = {http://dml.mathdoc.fr/item/hal-00000428}
}
Guirardel, Vincent. Limit groups and groups acting freely on R^n-trees.. HAL, Tome 2004 (2004) no. 0, . http://gdmltest.u-ga.fr/item/hal-00000428/