Response of a system of passive or active particles to periodic forcing

The presence of active, persistent forces in various biological and artificial systems changes how those systems behave when forced. We present a minimal model of a system of passive or active swimmers driven on the boundaries by a time-dependent forcing. We extract the linear response functions of the system and interpret them in terms of the storage and dissipation of energy through the particles within the system. We find that while a slowly driven active system responds similar to a passive system with a redefined diffusion constant, a rapidly driven active system exhibits a new behavior that may be related to a change in the motoring activity of the active particles due to the forcing.