  In many integrable models static (equal time) correlation functions of local
observables after a quantum quench relax to stationary values, which are
described by a generalized Gibbs ensemble (GGE). Here we establish that the
same holds true for dynamic (non equal time) correlation functions. More
generally we show that in the absence of long-range interactions in the final
Hamiltonian, the dynamics is determined by the same ensemble that describes
static correlations. When the latter is a GGE the basic form of the fluctuation
dissipation theorem holds, although the absorption and emission spectra are not
simply related as in the thermal case. For quenches in the transverse field
Ising chain (TFIC) we derive explicit expressions for the time evolution of
dynamic order parameter correlators after a quench.
