On finite-index extensions of subgroups of free groups

• Tipo: Artigo em Revista Científica Internacional
• Data: 2010

Autores

Pedro V. Silva (Autor) FCUP; Pascal Weil (Autor) Outra

Revista

Título: Journal of Group Theory

Vol. 13 Nº 3

Páginas: 365-381

ISSN: 1433-5883

Editora: Walter De Gruyter

Indexação

ISI Web of Knowledge - 1 Citação

ISI Web of Science

Scopus - 1 Citação

Classificação Científica

FOS: Ciências exactas e naturais > Matemática

Outras Informações

ID Authenticus: P-003-726

DOI: 10.1515/jgt.2009.055

Abstract (EN): We study the lattice of finite-index extensions of a given finitely generated subgroup H of a free group F. This lattice is finite and we give a combinatorial characterization of its greatest element, which is the commensurator of H. This characterization leads to a fast algorithm to compute the commensurator, which is based on a standard algorithm from automata theory. We also give a sub-exponential and super-polynomial upper bound for the number of finite-index extensions of H, and we give a language-theoretic characterization of the lattice of finite-index subgroups of H. Finally, we give a polynomial-time algorithm to compute the malnormal closure of H.

Idioma: Inglês

Tipo (Avaliação Docente): Científica

Nº de páginas: 17