title: The non-Gaussian tops and tails of diffusing boomerangs.
abstract: Experiments involving the two-dimensional passive diffusion of colloidal boomerangs tracked off their centre of mobility have shown striking non-Gaussian tails in their probability distribution function [Chakrabarty et al., Soft Matter, 2016, 12, 4318]. This in turn can lead to anomalous diffusion characteristics, including mean drift. In this paper, we develop a general theoretical explanation for these measurements. The idea relies on calculating the two-dimensional probability densities at the centre of mobility of the particle, where all distributions are Gaussian, and then transforming them to a different reference point. Our model clearly captures the experimental results, without any fitting parameters, and demonstrates that the one-dimensional probability distributions may also exhibit strongly non-Gaussian tops. These results indicate that the choice of tracking point can cause a considerable departure from Gaussian statistics, potentially causing some common modelling techniques to fail.
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, University of Cambridge, UK. e.lauga@damtp.cam.ac.uk.
authors.forename: Lyndon
authors.initials: L
authors.lastname: Koens
authors.forename: Maciej
authors.initials: M
authors.lastname: Lisicki
authors.forename: Eric
authors.initials: E
authors.lastname: Lauga