The Physics of Cold Active Matter: on how time-independent disorder affects the motion of self-propelled particles*

Most examples of natural active matter systems, if not all, take place in heterogeneous media. Despite this, most experimental and theoretical efforts have focused on homogeneous media and the impact of environmental heterogeneities on individual and collective properties of active systems has remained, up to recently, unexplored. Here, we will see that the physics of active systems in heterogeneous media is fundamentally different from the one in homogenous environments. For instance, in heterogeneous environments, spontaneous particle trapping of particles and sub-diffusion can occur, while long-range order of two-dimensional polar active liquids is not possible. Furthermore, in the absence of dynamic noise, it is possible to show that when the equations of motion exhibit a Hamiltonian structure, particle trapping cannot occur, while the presence of attractors in these equations indicates the asymptotic convergence of particle trajectories to bounded areas in space, i.e. traps.

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F. Peruani and I. S. Aranson, Phys. Rev. Lett. 120, 238101 (2018)
O. Chepizhko and Fernando Peruani, Phys. Rev. Lett. 111, 160604 (2013)
O. Chepizhko, E.G. Altmann, and F. Peruani, Phys. Rev. Lett. 110, 238101 (2013)