  Motivated by recent experiments of exceptional accuracy, we study numerically
the spin-glass dynamics in a film geometry. We cover all the relevant time
regimes, from picoseconds to equilibrium, at temperatures at and below the 3D
critical point. The dimensional crossover from 3D to 2D dynamics, that starts
when the correlation length becomes comparable to the film thickness, consists
of four dynamical regimes. Our analysis, based on a Renormalization Group
transformation, finds consistent the overall physical picture employed by
Orbach et al. in the interpretation of their experiments.
