Counting cycles in labeled graphs: The nonpositive immersion property for one-relator groups
arXiv:1410.2579
Abstract
We prove a rank 1 version of the Hanna Neumann Theorem. This shows that every one-relator 2-complex without torsion has the nonpositive immersion property. The proof generalizes to staggered and reducible 2-complexes.
12 pages, 2 figures