Off equilibrium dynamics in the 3d-XY system

We investigate through Monte Carlo simulations the non-equilibrium behaviour of the three-dimensional XY-model quenched from a high temperature state to its ferromagnetic and critical phases. The two-times autocorrelation and response functions are determined in the asymptotic (scaling) regime, from which the nonequilibrium exponents $\lambda$ and critical $\lambda^c$ are extracted. The form of the scaling function is in agreement with the prediction of local scale-invariance. The so-called limit fluctuation-dissipation ratio $X_\infty$ is shown to vanish in the ordered phase and to reach a constant value around 0.43 for the critical quench.