Displaying similar documents to “On an algorithm to decide whether a free group is a free factor of another”

An automata-theoretic approach to the study of the intersection of two submonoids of a free monoid

Laura Giambruno, Antonio Restivo (2008)

RAIRO - Theoretical Informatics and Applications

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We investigate the intersection of two finitely generated submonoids of the free monoid on a finite alphabet. To this purpose, we consider automata that recognize such submonoids and we study the product automata recognizing their intersection. By using automata methods we obtain a new proof of a result of Karhumäki on the characterization of the intersection of two submonoids of rank two, in the case of prefix (or suffix) generators. In a more general setting, for an arbitrary number...

Computing the prefix of an automaton

Marie-Pierre Béal, Olivier Carton (2000)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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Free group languages : rational versus recognizable

Pedro V. Silva (2004)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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We provide alternative proofs and algorithms for results proved by Sénizergues on rational and recognizable free group languages. We consider two different approaches to the basic problem of deciding recognizability for rational free group languages following two fully independent paths: the symmetrification method (using techniques inspired by the study of inverse automata and inverse monoids) and the right stabilizer method (a general approach generalizable to other classes of groups)....

Forbidden factors and fragment assembly

F. Mignosi, A. Restivo, M. Sciortino (2001)

RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications

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In this paper methods and results related to the notion of minimal forbidden words are applied to the fragment assembly problem. The fragment assembly problem can be formulated, in its simplest form, as follows: reconstruct a word w from a given set I of substrings (fragments) of a word w . We introduce an hypothesis involving the set of fragments I and the maximal length m ( w ) of the minimal forbidden factors of w . Such hypothesis allows us to reconstruct uniquely the word w from the set...

Free and non-free subgroups of the fundamental group of the Hawaiian Earrings

Andreas Zastrow (2003)

Open Mathematics

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The space which is composed by embedding countably many circles in such a way into the plane that their radii are given by a null-sequence and that they all have a common tangent point is called “The Hawaiian Earrings”. The fundamental group of this space is known to be a subgroup of the inverse limit of the finitely generated free groups, and it is known to be not free. Within the recent move of trying to get hands on the algebraic invariants of non-tame (e.g. non-triangulable) spaces...