Brendan Goldsmith * and Luigi Salce When the intrinsic algebraic entropy is not really intrinsic

DOI 10.1515/taa-2015-0005 Received August 20, 2014; accepted August 16, 2015 Abstract: The intrinsic algebraic entropy ̃︂ ent(φ) of an endomorphism φ of an Abelian group G can be computed using fully inert subgroups of φ-invariant sections of G, instead of the whole family of φ-inert subgroups. For a class of groups containing thegroupsof finite rank, aswell as those groupswhichare trajectories of finitely generated subgroups, it is proved that only fully inert subgroups of the group itself are needed to computẽ︂ ent(φ). Examples show how the situation may be quite different outside of this class.