Abstract
The aim of this paper is to unify the points of view of three recent and independent papers (Ventura 1997, Margolis, Sapir and Weil 2001 and Kapovich and Miasnikov 2002), where similar modern versions of a 1951 theorem of Takahasi were given. We develop a theory of algebraic extensions for free groups, highlighting the analogies and differences with respect to the corresponding classical field-theoretic notions, and we discuss in detail the notion of algebraic closure. We apply that theory to the study and the computation of certain algebraic properties of subgroups (e.g., being malnormal, pure, inert or compressed, being closed in certain profinite topologies) and the corresponding closure operators. We also analyze the closure of a subgroup under the addition of solutions of certain sets of equations.
This article originates from the Barcelona conference.
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© 2007 Birkhäuser Verlag Basel/Switzerland
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Miasnikov, A., Ventura, E., Weil, P. (2007). Algebraic Extensions in Free Groups. In: Arzhantseva, G.N., Burillo, J., Bartholdi, L., Ventura, E. (eds) Geometric Group Theory. Trends in Mathematics. Birkhäuser Basel. https://doi.org/10.1007/978-3-7643-8412-8_12
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DOI: https://doi.org/10.1007/978-3-7643-8412-8_12
Publisher Name: Birkhäuser Basel
Print ISBN: 978-3-7643-8411-1
Online ISBN: 978-3-7643-8412-8
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