Alladi Ramakrishnan Hall

Quantum mechanics-like behaviour of a classical object: a droplet walking on a vertically vibrated liquid surface

Saroj Nandi

MPIPKS, Dresden, Germany

In a series of experiments by Fort et al [Nature 437, 208 (2005)], a liquid, taken in a flat

square cell, is vibrated at a frequency close to but below the Farady instability. When a

droplet of the same liquid is placed on the liquid surface, it can keep on bouncing forever.

When the amplitude of vibration exceeds a critical value, the droplet starts walking on

the liquid surface in a rectilinear motion. As the droplet walks, it emanates waves as it

interacts with the surface and it seems to be riding on its own waves. The moving droplet

along with the associated wave have been termed together as a “walker”. Interestingly, the

walker shows behaviours that are reminiscent of the quantum world, like quantization of

the probability of particle position, diffraction, interference pattern, tunneling etc. We have

developed a hydrodynamic theory to understand this interesting phenomenon. In this talk,

I will first briefly discuss the experiment and then present our theory, its predictions and

possible generalization to a larger class of phenomena.