Finite automata for Schreier graphs of virtually free groups

Abstract

The Stallings construction for f.g. subgroups of free groups is generalized by introducing the concept of Stallings section, which allows efficient computation of the core of a Schreier graph based on edge folding. It is proved that the groups that admit Stallings sections are precisely the f.g. virtually free groups, this is proved through a constructive approach based on Bass–Serre theory. Complexity issues and applications are also discussed.