Mobility Anisotropy Reshapes Self-Propelled Motion

Abstract

We obtain exact closed-form moments for a harmonically trapped self-propelled particle with anisotropic translational mobility in two dimensions. At high persistence, the mean and MSD develop a quasi-steady plateau with vanishing fluctuations, after which the MSD relaxes in a second step. The steady excess kurtosis is negative and nonmonotonic in the mechanical-to-rotational timescale ratio, and the particle is pushed beyond the activity-confinement ring. The non-monotonic kurtosis is specific to strong mobility anisotropy - as in wheeled or gliding particles, not bulk hydrodynamic rods - whereas the two-step MSD remains visible whenever transverse relaxation is slow compared with rotational diffusion.

arXiv comment8 pages, 4 figures (main text with End Matter); Supplemental Material: 13 pages, 2 figures, 2 tables