Collective response of an array of rotating particles to fluctuating confining forces

We study the influence of fluctuations of confining forces on the rotation patterns in a dense array of cylinders. Our theoretical studies are motivated by new results from detailed time-resolved experimental measurements. In order to calculate the system’s evolution in time at each moment, a molecular-dynamics code adapted to the system is developed. The numerical procedure is tested by a comparison with rigorous predictions derived analytically. The chain’s reaction on oscillating confining forces is analyzed numerically for different typical cases. Our theoretical results reproduce the striking features of the experimental data. A quantitative analysis of the experimental data is performed by a computation of their power spectrum and of spatial and temporal correlation functions. From our comparison of the theoretical and experimental results we conclude that the experimental rotation patterns result of random superpositions of different steady-state patterns (“collective random walk”).