Graphs, free groups and the Hanna Neumann conjecture

Abstract A new bound for the rank of the intersection of finitely generated subgroups of a free group is given, formulated in topological terms, and in the spirit of Stallings [J. R. Stallings. Topology of finite graphs. Invent. Math. 71 (1983), 551–565.]. The bound is a contribution to the strengthened Hanna Neumann conjecture.

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