We construct an efficient model for graphs of finitely generated subgroups of free groups. Using this we give a very short proof of Dicks’s reformulation of the strengthened Hanna Neumann Conjecture as the Amalgamated Graph Conjecture. In addition, we answer a question of Culler and Shalen on ranks of intersections in free groups. The latter has also been done independently by R P Kent IV.
Louder, Larsen  1 ; McReynolds, D B  2
@article{10_2140_agt_2009_9_327,
author = {Louder, Larsen and McReynolds, D B},
title = {Graphs of subgroups of free groups},
journal = {Algebraic and Geometric Topology},
pages = {327--335},
year = {2009},
volume = {9},
number = {1},
doi = {10.2140/agt.2009.9.327},
url = {http://geodesic.mathdoc.fr/articles/10.2140/agt.2009.9.327/}
}
Louder, Larsen; McReynolds, D B. Graphs of subgroups of free groups. Algebraic and Geometric Topology, Tome 9 (2009) no. 1, pp. 327-335. doi: 10.2140/agt.2009.9.327
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[4] , Krull dimension for limit groups III: Scott complexity and adjoining roots to finitely generated groups
[5] , Topology of finite graphs, Invent. Math. 71 (1983) 551
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