Évènement

In this talk, which is for a wide audience, I shall sketch the development of a body of ideas concerning the geometry and complexity of subgroups of direct products of groups, which was developed in a long and joyful collaboration with Hamish Short, Gilbert Baumslag, Jim Howie and Chuck Miller, starting in the 1990s. These ideas greatly extended what is known about subgroups of direct products of hyperbolic groups; they provided new tools for deciding which groups can be finitely presented (the 1-2-3 Theorem and the VSP Theorem); and they led to a complete classification of finitely presented, residually free groups. Groups will be the main objects of study, but geometry is always close at hand.