作者:DICKS, W
摘要: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.
作者:BESSON, G; COURTOIS, G; GALLOT, S
作者单位:Ecole Normale Superieure de Lyon (ENS de LYON); Institut Polytechnique de Paris; Ecole Polytechnique; Centre National de la Recherche Scientifique (CNRS)
作者:FINTUSHEL, R; STERN, RJ
作者单位:University of California System; University of California Irvine