  Pristine monolayer graphene exhibits very poor screening because the density
of states vanishes at the Dirac point. As a result, charge relaxation is
controlled by the effects of zero-point motion (rather than by the Coulomb
interaction) over a wide range of parameters. Combined with the fact that
graphene possesses finite intrinsic conductivity, this leads to a regime of
relaxation described by a non-linear diffusion equation with a diffusion
coefficient that diverges at zero charge density. Some consequences of this
fast diffusion are self-similar superdiffusive regimes of relaxation, the
development of a charge depleted region at the interface between electron- and
hole-rich regions, and finite extinction times for periodic charge profiles.
