  In a theoretical and simulation study, active Brownian particles (ABPs) in
three-dimensional bulk systems are exposed to time-varying sinusoidal activity
waves that are running through the system. A linear response (Green-Kubo)
formalism is applied to derive fully analytical expressions for the torque-free
polarization profiles of the particles. The activity waves induce fluxes that
strongly depend on the particle size and may be employed to de-mix mixtures of
ABPs or to drive the particles into selected areas of the system.
Three-dimensional Langevin dynamics simulations are carried out to verify the
accuracy of the linear response formalism, which is shown to work best when the
particles are small (i.e., highly Brownian) or operating at low activity
levels.
