The boundary of the complex of free factors
  We give a description of the boundary of a complex of free factors that is analogous to E. Klarreich's description of the boundary of a curve complex. The argument uses the geometry of folding paths developed by Bestvina and Feighn as well as structural results about very small trees developed by Coulbois, Hilion, Lustig, and Reynolds. 
Mladen Bestvina and Patrick Reynolds
math.GR math.GT