Aperiodic Order: Tilings, Substitutions, and Diffraction I & II

Robert Moody

Tilings, logic, quasicrystals, discrete geometry, long-range order, and diffraction all come together in a remarkable confluence of ideas. In the first (general) talk, we will begin with some of the unexpected history of the subject of Aperiodic Order and discuss some of the mathematics that it has generated, as well as some of its outstanding problems. We will touch on many areas: geometry, topology, measure theory, dynamical systems, and algebra. However, the great thing about the subject is the number of nice pictures that are relevant to it, and I will show lots of them! One of the interesting problems in this subject is to understand what it means for a point set to be pure point diffractive. In the second talk I would like to talk more about diffraction and go into some details about what is known in the case of substitution systems and how we know it. This talk will require a little more mathematical background, but I will stay away from a lot of technical details.