A decade ago, Yves Couder and Emmanuel Fort discovered that droplets walking on a vibrating fluid bath exhibit several features previously thought to be exclusive to the microscopic, quantum realm. The walking droplets propel themselves by virtue of a resonant interaction with their own wavefield, and so represent the first macroscopic realization of a pilot-wave system of the form proposed for microscopic quantum dynamics by Louis de Broglie in the 1920s. New experimental and theoretical results in turn reveal and rationalize the emergence of quantization and quantum-like statistics from this hydrodynamic pilot-wave system in a number of `closed’ settings, specifically, when the droplet motion is constrained by either boundaries or an applied force. The limitations of the walking droplet system as a hydrodynamic quantum analog have become apparent in open systems, including single-walker diffraction through slits. A number of novel directions involving walker-bottom-topography interactions will be discussed, including hydrodynamic spin lattices and a hydrodynamic analog of the `quantum mirage’ effect.
Biography: John Bush is a Professor of Mathematics at MIT, where he directs the Applied Math Laboratory and is currently Associate Department Head. His work concerns the mathematical description of systems arising in the physical world, in either natural or laboratory settings. A specialist in fluid dynamics, he first research was on geophysical and environmental flows, but he now focuses on surface tension-driven phenomena, their applications in biology, and hydrodynamic quantum analogues.