Finitely generated subgroups of amalgamated free products and HNN groups
Daniel E. Cohen
Abstract
Open-access reader
Daniel E. Cohen
Abstract
Open-access reader
Abstract The theory of groups acting on trees due to Bass and Serre (1969) is applied to simplify some results of Burns (1972, 1973) giving conditions under which an amalgamated free product or HNN extension has the properties that any finitely generated subgroup containing an infinite subnormal subgroup must have finite index and that the intersection of two finitely generated subgroups is finitely generated.
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Abstract The theory of groups acting on trees due to Bass and Serre (1969) is applied to simplify some results of Burns (1972, 1973) giving conditions under which an amalgamated free product or HNN extension has the properties that any finitely generated subgroup containing an infinite subnormal subgroup must have finite index and that the intersection of two finitely generated subgroups is finitely generated.
Key concepts: Free product, Mathematics, Finitely-generated abelian group, Stallings theorem about ends of groups, Intersection (aeronautics), Finitely generated group, Product (mathematics), Extension (predicate logic)