, Volume 117, Issue 1, pp 373-389

Equivalence of the strengthened Hanna Neumann conjecture and the amalgamated graph conjecture

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Summary

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.

Oblatum 30-VIII-1993