## Hatfest: Celebrating the Discovery of an Aperiodic Monotile

**Date:**
20 - 21 July 2023

**Location: ** University of Oxford

**Event type:**
Public Engagement

**Organisers: ** Felix Flicker (Cardiff), Nick Jones (Oxford), Henna Koivusalo (Bristol), Mike Whittaker (Glasgow)

The theory of tilings in the plane touches on diverse areas of mathematics, physics and beyond. Aperiodic sets of tiles, such as the famous Penrose tiling that you see as you walk into the Mathematical Institute at the University of Oxford, admit tilings of the plane without any translational symmetry. The Penrose tiling is made of two elementary shapes, or tiles, and mathematicians have long wondered about the existence of a single tile that could tile the plane aperiodically. Earlier this year such a shape was discovered: the hat! This hat turned out to be the first of a whole family, and is being celebrated across a two-day meeting in Oxford.

At his public talk, Chaim Goodman-Strauss (National Museum of Mathematics / University of Arkansas), one of the authors of this new work, will give an overview of the hat. This will be followed by a panel discussion featuring Craig Kaplan (University of Waterloo), Marjorie Senechal (Smith College) and Sir Roger Penrose (University of Oxford) as well as Chaim Goodman-Strauss. The discussion, about the impact of this new discovery and future directions, will be chaired by Henna Koivusalo (University of Bristol).

The first day of this event will contain talks and workshops aimed at the public, while the second will contain accessible talks aimed at the broadest possible mathematical audience. There will be artworks on display and activities to undertake for the duration of the event.

Videos of the talks can be seen on YouTube.