Enhancement of swimmer diffusion through regular kicks: analytic mapping of a scale independent parameter space

TL;DR

This paper analytically and numerically demonstrates that periodic propulsion velocity profiles in active particles can significantly enhance their long-term diffusion compared to constant velocity, especially with exponential decay pulses.

Contribution

It introduces a scale-independent parameter space mapping showing how periodic velocity profiles increase diffusion, providing new insights into active particle behavior.

Findings

Periodic propulsion profiles increase diffusion coefficients.

Exponential decay velocity pulses can arbitrarily enhance diffusion.

Analytic and numerical methods confirm diffusion enhancement.

Abstract

Depending on their mechanism of self-propulsion, active particles can exhibit a time-dependent, often periodic, propulsion velocity. The precise propulsion velocity profile determines their mean square displacement and their effective diffusion coefficient at long times. Here we demonstrate that any periodic propulsion profile results in a larger diffusion coefficient than the corresponding case with constant propulsion velocity. We investigate in detail the case of periodic exponentially decaying velocity pulses, expected in propulsion mechanisms based on sudden absorption of finite amounts of energy. We show both analytically and with numerical simulations that in these cases the effective diffusion coefficient can be arbitrarily enhanced with respect to the case with constant velocity equal to the average speed. Our results may help interpret in a new light observations on the diffusion enhancement of active particles.