On an algorithm to decide whether a free group is a free factor of another
Pedro V. Silva, Pascal Weil (2007)
RAIRO - Theoretical Informatics and Applications
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We revisit the problem of deciding whether a finitely generated subgroup is a free factor of a given free group . Known algorithms solve this problem in time polynomial in the sum of the lengths of the generators of and exponential in the rank of . We show that the latter dependency can be made exponential in the rank difference rank - rank, which often makes a significant change.