  Recent experimental studies, both in vivo and in vitro, have revealed that
membrane components that bind to the cortical actomyosin meshwork are driven by
active fluctuations, whereas membrane components that do not bind to cortical
actin are not. Here we study the statistics of density fluc- tuations and
dynamics of particles advected in an active quasi-two dimensional medium
comprising self-propelled filaments with no net orientational order, using a
combination of agent-based Brow- nian dynamics simulations and analytical
calculations. The particles interact with each other and with the
self-propelled active filaments via steric interactions. We find that the
particles show a tendency to cluster and their density fluctuations reflect
their binding to and driving by the active filaments. The late-time dynamics of
tagged particles is diffusive, with an active diffusion coefficient that is
independent of (or at most weakly-dependent on) temperature at low
temperatures. Our results are in qualitative agreement with the experiments
mentioned above. In addition, we make predictions that can be tested in future
experiments.
