  It is expected that thermalization may be described within gauge/gravity
duality by considering time-dependent configurations on the gravity side of the
correspondence, for instance a gravitational collapse of a matter configuration
in Anti-de Sitter space. As a step towards the ambitious goal of describing
such a configuration, we investigate a simple time-dependent toy model in which
a mirror moves in the radial direction of Anti-de Sitter space. For this
configuration, we establish a procedure for calculating two-point functions of
scalar fluctuations, based on a WKB approximation. We test our method on two
sample trajectories for the mirror, and find that the singularity structure of
the two-point functions is in agreement with geometric optics.
