Artin groups with big outer automorphism groups

Artin groups are a rich class of groups generalising braid groups and closely related to Coxeter groups. For each large-type triangle-free Artin group A, I will describe a contractible deformation space with an action of Out(A). This space is a useful tool for studying Out(A), especially when it is "big". I will discuss how to use this space to show that outer automorphism groups of such Artin groups are either virtually abelian or contain a non-abelian free subgroup, and how this dichotomy is characterised in the Artin group's defining graph.