Absence of jamming in ant trails: Feedback control of self propulsion and noise

TL;DR

This paper models ant trail movement as self-propelled particles with feedback control, explaining the absence of jamming at high densities and predicting a phase transition to a single large cluster.

Contribution

It introduces a feedback-controlled self-propulsion model that replicates experimental ant traffic behavior and predicts a non-equilibrium phase transition.

Findings

Ants maintain constant collective velocity at high densities.

Distance headway distribution peaks within clusters, independent of density.

A first-order transition leads to a single large cluster at a threshold density.

Abstract

We present a model of ant traffic considering individual ants as self-propelled particles undergoing single file motion on a one-dimensional trail. Recent experiments on unidirectional ant traffic in well-formed natural trails showed that the collective velocity of ants remains approximately unchanged, leading to absence of jamming even at very high densities [ John et. al., Phys. Rev. Lett. 102, 108001 (2009) ]. Assuming a feedback control mechanism of self-propulsion force generated by each ant using information about the distance from the ant in front, our model captures all the main features observed in the experiment. The distance headway distribution shows a maximum corresponding to separations within clusters. The position of this maximum remains independent of average number density. We find a non-equilibrium first order transition, with the formation of an infinite cluster at a threshold density where all the ants in the system suddenly become part of a single cluster.