  As a particle moves through a fluid, it may generate a laminar wake behind
it. In the gauge-string duality, we show that such a diffusion wake is created
by a heavy quark moving through a thermal plasma and that it has a universal
strength when compared to the total drag force exerted on the quark by the
plasma. The universality extends over all asymptotically anti-de Sitter
supergravity constructions with arbitrary scalar matter. We discuss how these
results relate to the linearized hydrodynamic approximation and how they bear
on our understanding of di-hadron correlators in heavy ion collisions.
