An effective version of Stallings' theorem in the case of context-free groups

  • Géraud Sénizergues
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 700)


We give an algorithm producing from every p.d.a. M recognizing the word-problem for an infinite group G, a decomposition of G as an amalgamated product (with finite amalgamated subgroups) or as an HNN-extension (with finite associated subgroups).This algorithm has an elementary time-complexity.This result allows us to show that the isomorphism-problem for finitely generated virtually-free groups is primitive recursive, thus improving the decidability result of [Krstic,1989].


context-free groups pushdown automata Cayley graph Thue-systems complexity graph of groups 


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Copyright information

© Springer-Verlag Berlin Heidelberg 1993

Authors and Affiliations

  • Géraud Sénizergues
    • 1
  1. 1.LaBri and UER Math-infoUniversité Bordeaux1Talence Cedex

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