I consider the non-equilibrium time evolution after a "quantum quench": an isolated many-particle system is initially prepared in its ground state and at time t=0 a parameter such as a magnetic field or an interaction strength is changed suddenly. I discuss realisations of such effects in systems of ultra-cold trapped atoms and review general expectations regarding the late-time behaviour of these systems. Interestingly, in the thermodynamic limit the expectation values of local observables relax to time-independent values, even though the system is not coupled to a bath. I show that conservation laws affect the non equilibrium dynamics and the stationary behaviour very strongly and present detailed results for the "Ising model" of quantum quenches, the transverse-field Ising chain.
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