Many-body Dynamics and Universality in Flatland

One of the great successes of the last-century physics was recognising that many complex and seemingly disparate many-particle systems are fundamentally alike. This allowed the classification of the equilibrium states of matter into universality classes, based on their basic properties such as symmetries and the form of the interparticle interactions. At the heart of this classification is the universal collective behaviour, insensitive to the microscopic details, displayed by systems close to phase transitions. A grand challenge for modern physics is to achieve such a feat for the far richer world of the non-equilibrium collective phenomena. In recent years, theories that posit universal features of far-from-equilibrium many-body dynamics, common to systems as diverse as quantum magnets and the quark-gluon plasma, have been receiving support from experiments on the highly tuneable ultracold atomic gases. Our ambition is to make a leading contribution to this worldwide effort, through a series of coordinated experiments on homogeneous atomic gases in two-dimensional (2D) ‘Flatland’ geometry. Specifically, we will study in parallel three paradigmatic problems – the dynamics of the topological Berezinskii-Kosterlitz-Thouless phase transition, turbulence in driven systems, and the universal spatiotemporal scaling behaviour in isolated quantum systems far from equilibrium. Each of these topics is fascinating and of fundamental importance in its own right, but beyond that we will experimentally establish an emerging picture that coherently connects them.