Solvable models for entropic quasicrystals
- Event time: 1:00pm
- Event date: 6th May 2002
- Speaker: Bernard Nienhuis (University of Edinburgh)
- Location: Room 2511, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB
Beside the well known crystallographic solid, nature has in the last two decades revealed to us another solid phase: the quasicrystal. It behaves in almost all aspects as an ordinary crystal: it can be cleaved only in certain discrete directions, it grows in nicely symmetric structures, and its diffraction patterns consist of Bragg peaks. The defining difference with ordinary crystals is that its rotational symmetries are forbidden by the theory of crystallography. Quasicrystals seem to show both periodicity and rotational symmetry, but mathematically these symmetries are not compatible. In this seminar I present some tiling models that show these same properties of physical quasicrystals, albeit in two dimensions. A tiling is a complete and non-overlapping covering of space by copies of a few geometrical objects. Here they are studied as statistical models, so that a whole ensemble of tilings is considered. They are quite close to dense packings of hard disks of two different sizes. We will focus on cases where the thermodynamic quantities can be calculated exactly.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..