  We examine the validity of fluctuation-dissipation relations in isolated
quantum systems taken out of equilibrium by a sudden quench. We focus on the
dynamics of trapped hard-core bosons in one-dimensional lattices with dipolar
interactions whose strength is changed during the quench. We find that
fluctuation-dissipation relations hold if the system is nonintegrable after the
quench. They also hold if the system is integrable after the quench if the
initial state is an equilibrium state of a nonintegrable Hamiltonian. However,
they fail if the system is integrable both before and after quenching.
