Effect of asymmetric tumble distributions on motility-induced phase separation

Determine whether the effective chirality introduced by an asymmetric tumble distribution suppresses motility-induced phase separation in interacting run-and-tumble particles, and characterize how this effect depends on the complete Fourier spectrum of the tumble-angle distribution.

Background

The paper develops a Doi–Peliti field theory for run-and-tumble particles with a general, non-uniform tumble-angle distribution. The first Fourier mode determines effective persistence and chirality, while higher Fourier modes influence higher-order spatial observables. The framework is proposed as a starting point for studying interacting particles with non-trivial tumble statistics.

Motility-induced phase separation is established for run-and-tumble particles with uniform tumbling. The unresolved issue is whether the effective chirality generated by an asymmetric tumble distribution suppresses this collective phase behavior, as has been observed for chiral active Brownian particles, and whether the result is controlled solely by the effective chirality or also by higher Fourier modes of the tumble distribution.

References

In the uniform case, motility-induced phase separation (MIPS) is a well-established collective phenomenon ; whether the effective chirality $\Omega$ introduced by an asymmetric tumble distribution suppresses MIPS, as is the case for chiral ABPs , and how this depends on the full Fourier content of $\Pi(\psi)$, remains an open question.

— Run-and-tumble particles with preferred reorientation  (2608.23519 - Britton et al., 24 Aug 2026) in Discussion and outlook, Section 5