Scarred quantum wave. Computer model showing the paths taken by a wave trapped inside a stadium- shaped cavity. The paths show the movement of a particle which is behaving like a wave (showing wave-particle duality), as it bounces around the cavity. The pattern has features characteristic of classical and quantum mechanics. It is similar to a random quantum wave, formed by randomly adding together waves travelling in all directions. However, it is known as a scarred quantum wave, because it features classical periodic orbits (repeating paths) which give it symmetry, forming a double diamond". Modelled by Professor Eric Heller at Harvard University, USA."