## Séminaire Orléans

**Which distributions of matter diffract topologically?**

Johannes Kellendonk (Lyon)

Thursday 30 May 2013 14:00 - Orléans - Salle de Séminaire

**Résumé :**

The question of which distributions of matter diffract was naturally posed following the discovery of quasicrystals (for which Shechtman got the Nobelprize in chemistry 2011). The question may be formulated in mathematical terms and then related to the dynamical system defined by the point set of atomic positions of the matter. A priori the dynamical system is a measure dynamical system. But it turned out that for all examples used in quasicrystal physics, it is the TOPOLOGICAL variant of the dynamical system which is of importance. This means that diffractivity becomes a topological property. I will discuss how effectively the topological dynamical system of a point set describes the set and then answer the question in the title as far as I can.

**Liens :**