  The eukaryotic cell's cytoskeleton is a prototypical example of an active
material: objects embedded within it are driven by molecular motors acting on
the cytoskeleton, leading to anomalous diffusive behavior. Experiments tracking
the behavior of cell-attached objects have observed anomalous diffusion with a
distribution of displacements that is non-Gaussian, with heavy tails. This has
been attributed to "cytoquakes" or other spatially extended collective effects.
We show, using simulations and analytical theory, that a simple continuum
active gel model driven by fluctuating force dipoles naturally creates heavy
power-law tails in cytoskeletal displacements. We predict that this power law
exponent should depend on the geometry and dimensionality of where force
dipoles are distributed through the cell; we find qualitatively different
results for force dipoles in a 3D cytoskeleton and a quasi-two-dimensional
cortex. We then discuss potential applications of this model both in cells and
in synthetic active gels.
