Equivalence of the strengthened Hanna Neumann conjecture and the amalgamated graph conjecture
- Cite this article as:
- Dicks, W. Invent Math (1994) 117: 373. doi:10.1007/BF01232249
We show that Walter Neumann's strengthened form of Hanna Neumann's conjecture on the best possible upper bound for the rank of the intersection of two subgroups of a free group is equivalent to a conjecture on the best possible upper bound for the number of edges in a bipartite graph with a certain weak symmetry condition. We illustrate the usefulness of this equivalence by deriving relatively easily certain previously known results.