1.Department of Mathematics,University of Athens,Athens,Greece
Abstract:
We give necessary and sufficient conditions under which an HNN-extension with abelian base group or an amalgamated free product
of abelian groups is a Howson group (that is the intersection of any two finitely generated subgroups is finitely generated).
We describe HNN-extensions and amalgamated free products which are Howson groups without satisfying the Burns–Cohen statements.