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Graphs, free groups and the Hanna Neumann conjecture

Brent Everitt
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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 very much in the spirit of Stallings. The bound is a contribution to (although unfortunately not a solution of) the strengthened Hanna Neumann conjecture.

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Brent Everitt. 2007-10-16. Graphs, free groups and the Hanna Neumann conjecture. https://arxiv.org/abs/math/0701214

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