Abstract
The motion of self-propelled massive particles through a gaseous medium is dominated by inertial effects. Examples include vibrated granulates, activated complex plasmas and flying insects. However, inertia is usually neglected in standard models. Here, we experimentally demonstrate the significance of inertia on macroscopic self-propelled particles. We observe a distinct inertial delay between orientation and velocity of particles, originating from the finite relaxation times in the system. This effect is fully explained by an underdamped generalisation of the Langevin model of active Brownian motion. In stark contrast to passive systems, the inertial delay profoundly influences the long-time dynamics and enables new fundamental strategies for controlling self-propulsion in active matter.
Highlights
The motion of self-propelled massive particles through a gaseous medium is dominated by inertial effects
Using the mean squared displacements (MSDs) and velocity distributions, fitted by numerical and analytical results, we extract a unique set of parameters for the model
Our observations demonstrate the profound influence of inertia on the long- and short-time dynamics of self-propelled particles
Summary
The motion of self-propelled massive particles through a gaseous medium is dominated by inertial effects. We observe a distinct inertial delay between orientation and velocity of particles, originating from the finite relaxation times in the system This effect is fully explained by an underdamped generalisation of the Langevin model of active Brownian motion. We demonstrate that the inertia of self-propelled particles causes a significant delay between their orientation and velocity and increases the long-time diffusion coefficient through persistent correlations in the underdamped rotational motion. Standard models, such as the Vicsek-model[20] and active Brownian motion[21] cannot explain this behaviour as they neglect inertia. We derive analytic solutions for the short- and long-time behaviour of the MSD and prove that the long-time diffusion coefficient explicitly depends on the moment of inertia
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