Diffusion in an expanding plasma using AdS/CFT

We consider the diffusion of a non-relativistic heavy quark of fixed mass M, in a one-dimensionally expanding and strongly coupled plasma using the AdS/CFT duality. The Green's function constructed around a static string embedded in a background with a moving horizon, is identified with the noise correlation function in a Langevin approach. The (electric) noise decorrelation is of order 1/T(τ) while the velocity de-correlation is of order MD(τ)/T(τ). For MD > 1, the diffusion regime is segregated and the energy loss is Langevin-like. The time dependent diffusion constant D(τ) asymptotes its adiabatic limit 2/π(λ) ^1/2T(τ) when τ/τ ₀ = (1/3η ₀τ ₀) ³ where η ₀ is the drag coefficient at the initial proper time τ ₀.