Title: Noise and diffusion in vibrated self-propelled granular particles

Author (Talk): Lee Walsh, University of Massachusetts, Amherst

Abstract:

Granular materials are often used as good laboratory models for active matter systems. The observed phenomena are often theoretically treated in the framework of the active Brownian particle model. Our goal in this work is to make a detailed comparison between single-particle behavior in an experiment, and the assumptions and predictions of this model. We study hard granular particles confined to a plane and fluidized by vibration. The particle shapes are designed to have directed motion of various kinds, but we focus on polar particles in the dilute limit for this study. We measure both short- and long-time behavior of the experimental particles, and compare these to the assumptions of the model regarding short-time noise, and to the predictions of the model for long-time drift. We have studied this behavior as a function particle shape as well as driving parameters (frequency and amplitude) and confinement geometry. I will discuss the need to extend the ABP model by adding correlations to the noise. Finally, I will report on the validity of assumptions concerning spatial correlations in the noise.