Periodic elements in finite type Artin-Tits groups and stability conditions

Abstract: Periodic elements in finite type Artin--Tits groups are elements some positive power of which is central. We give a dynamical characterisation of periodic elements via their action on the corresponding 2-Calabi--Yau category and on its space of (fusion equivariant) Bridgeland stability conditions. The main theorem is that an element $\beta$ is periodic if and only if $\beta$ has a fixed point in the stability manifold.