
Imagination and the Impossible
Two more sources I’d like to draw from for this fall’s maths for designerscourse: 1. Geometry and the Imagination A fantastic collection of handouts for a two week summer workshop entitled â€™Geometry and the Imaginationâ€™, led by John Conway, Peter Doyle, Jane Gilman and Bill Thurston at the Geometry Center in Minneapolis, June 1991, based […]

de Bruijn’s pentagrids (2)
Last time we’ve seen that de Bruijn’s pentagrids determined the vertices of Penrose’s P3aperiodic tilings. These vertices can also be obtained by projecting a window of the standard hypercubic lattice $\mathbb{Z}^5$ by the cutandprojectmethod. We’ll bring in representation theory by forcing this projection to be compatible with a $D_5$subgroup of the symmetries of $\mathbb{Z}^5$, which…

de Bruijn’s pentagrids
In a Rhombic tiling (aka a Penrose P3 tiling) we can identify five ribbons. Opposite sides of a rhomb are parallel. We may form a ribbon by attaching rhombs along opposite sides. There are five directions taken by sides, so there are five families of ribbons that do not intersect, determined by the side directions.…

Penrose’s aperiodic tilings
Around 1975 Sir Roger Penrose discovered his aperiodic P2 tilings of the plane, using only two puzzle pieces: Kites (K) and Darts (D) The inner angles of these pieces are all multiples of $36^o = \tfrac{180^o}{5}$, the short edges have length $1$, and the long edges have length $\tau = \tfrac{1+\sqrt{5}}{2}$, the golden ratio. These…

Conway’s musical sequences
Before we’ll come to applications of quasicrystals to viruses it is perhaps useful to illustrate essential topics such as deflation, inflation, aperiodicity, local isomorphism and the cutand project method in the simplest of cases, that of $1$dimensional tilings. We want to tile the line $\mathbb{R}^1$ with two kinds of tiles, short ($S$) and ($L$) long…

GoV 2 : Viruses and quasicrystals
If you look around for mathematical theories of the structure of viruses, you quickly end up with the work of Raidun Twarock and her group at the University of York. We’ve seen her proposal to extend the CasparKlug classification of viruses. Her novel idea to distribute proteins on the viral capsid along Penroselike tilings shouldn’t…

GoV 1 : Geometry of viruses
As you may have guessed from the symmetries of Covid19 post, I did spend some time lately catching up with the literature on the geometric structure and symmetries of viruses. It may be fun to run a little series on this. A virus is a parasite, so it cannot reproduce on its own and needs…

Penrose tiles in Helsinki
(image credit: Steve’s travels & stuff) A central street in Helsinki has been paved with Penrose tiles. (image credit: Sattuman soittoa) From a Finnish paper: “The street could also be an object to mathematical awe. The stone under one’s feet is embroidered with some profound geometry, namely, Penrose tiling. In 1974, a British mathematician Roger…

Penrose tilings and noncommutative geometry
Penrose tilings are aperiodic tilings of the plane, made from 2 sort of tiles : kites and darts. It is well known (see for example the standard textbook tilings and patterns section 10.5) that one can describe a Penrose tiling around a given point in the plane as an infinite sequence of 0’s and 1’s,…