Active Fractal Networks with Stochastic Force Monopoles and Force Dipoles

Motivated by the well-known fractal packing of chromatin, Rony Granek studies the Rouse-type dynamics of elastic fractal networks with embedded, stochastically driven, active force monopoles and force dipoles that are temporally correlated. Granek computes, analytically - using a general theoretical framework - and via Langevin dynamics simulations, the mean square displacement (MSD) of a network bead. Following a short time superdiffusive behavior, force monopoles yield anomalous subdiffusion with an exponent identical to that of the thermal system. In contrast, force dipoles do not induce subdiffusion, and the early superdiffusive MSD crosses over to a relatively small, system-size-independent saturation value.