Inventiones mathematicae

, Volume 108, Issue 1, pp 29–36

On the intersection of subgroups of a free group

  • Gábor Tardos

DOI: 10.1007/BF02100597

Cite this article as:
Tardos, G. Invent Math (1992) 108: 29. doi:10.1007/BF02100597


The Hanna Neumann Conjecture says that the intersection of subgroups of rankn+1 andm+1 of a free group has rank at mostnm+1. This paper proves the conjecture for the casem=1. (See Theorem 1.) Our methods imply that the strengthened Hanna Neumann Conjecture is also true in this case (Theorem 2′).

Copyright information

© Springer-Verlag 1992

Authors and Affiliations

  • Gábor Tardos
    • 1
    • 2
  1. 1.DIMACS CenterRutgers UniversityPiscatawayUSA
  2. 2.Mathematical Research InstituteHungarian Academy of SciencesHungary