  We present the first exact calculations of the time dependence of causal
correlations in driven nonequilibrium states in (2+1)-dimensional systems using
holography. Comparing exact results with those obtained from simple prototype
geometries that are parametrized only by a time dependent temperature, we find
that the universal slowly varying features are controlled just by the pump
duration and the initial and final temperatures only. We provide numerical
evidence that the locations of the event and apparent horizons in the dual
geometries can be deduced from the nonequilibrium causal correlations without
any prior knowledge of the dual gravity theory.
