Dynamical active particles in the overdamped limit

TL;DR

This paper extends the dynamical active particle model to the overdamped limit, demonstrating that active particles can still effectively move against friction by operating at slower speeds, aligning phenomenological models with physical mechanisms.

Contribution

It generalizes the dynamical active particle model to strongly dissipative environments, showing the mechanism's robustness in the overdamped regime.

Findings

Active particles can travel against friction in overdamped conditions.

The mechanism allows particles to move at slower speeds but cover similar distances.

Phenomenological models remain valid in viscous, highly damped environments.

Abstract

Mobile microscopic bodies, such as motile cells, can be modelled phenomenologically as ``active particles'' which can move against external forces by depleting an internal energy depot. The microscopic mechanisms underlying such ``active'' behavior must ultimately obey fundamental physics: energy depots must actually consist of dynamical degrees of freedom, such as chemical reaction coordinates, which in some way couple to the particle's motional degrees of freedom. As a step towards connecting phenomenological models with microscopic dynamical mechanisms, recent papers have studied the minimalistic dynamical mechanism of a ``dynamical active particle'', and shown how nonlinear couplings can allow steady energy transfer from depot to motion, even in the presence of weak dissipation. Most real active particles move through viscous environments, however, and are strongly damped. Here we therefore generalize the dynamical active particle into the overdamped regime. We find that its mechanism still operates, and in particular allows the overdamped active particle to travel just as far against friction as the undamped model, by moving at a slower average speed. Our results suggest that active particle phenomenology can indeed be consistent with comprehensible dynamical mechanisms, even in strongly dissipative environments.