Microscopic theory of soft run-and-tumble particles
Abstract
Soft, repulsive run-and-tumble particles display emergent effective interactions as they appear to stick to each other in spite of the absence of attractive forces. This effective attraction emerges at strong enough repulsion and large self-propulsion. Complementing a companion paper that characterises effective attraction between two soft run-and-tumble particles [Garcia-Millan et al., Effective attraction by repulsion (2026)], here we provide a thorough derivation of our microscopic theory, which is an exact representation of the particle dynamics. We report the systematic calculation of the effective interaction vertices iteratively, in a perturbation expansion about the interaction couplings, by adding, order by order, loop corrections. We use the effective interaction vertices to calculate the two-point correlation function, fully characterising the stationary state. Other observables, such as the structure factor, overlap probability and entropy production rate are calculated as well.
Keywords
Cite
@article{arxiv.2605.01422,
title = {Microscopic theory of soft run-and-tumble particles},
author = {Rosalba Garcia-Millan and Ziluo Zhang and Luca Cocconi and Marius Bothe and Letian Chen and Zigan Zhen and Gunnar Pruessner},
journal= {arXiv preprint arXiv:2605.01422},
year = {2026}
}
Comments
25 pages, 7 figures