Memory formation and evolution of the vortex configuration associated with random organization

We study the general phenomenon of randomorganization using a vortex system.When a periodic shearwith a small shear amplitude dinp is applied tomany-particle (vortex) assemblies with a random distribution, the particles (vortices) gradually self-organize to avoid future collisions and transform into an organized configuration. This is detected from the time-evolution of the voltageV t ( ) (average velocity) that increases towards a steady-state value. From the subsequent readoutmeasurements of V t ( )using various shear amplitudes, we find that the information of the input shear amplitude dinp is memorized in the configuration of the vortex distributions in the transient as well as the steady state, and that it is readable.We alsofind that the transient vortex configuration formed during random organization is notmicroscopically homogeneous but consists of disordered and organized regions.