Genevieve Walsh, Tufts University, Incoherent free-by-free groups
A group G is called coherent if every finitely generated subgroup of G is finitely presented. This is a property enjoyed by the fundamental groups of 3-manifolds, and it is deeply related to the geometry of the group. We show that free-by-free groups satisfying a particular homological criterion are incoherent. This class is large in…