Off equilibrium dynamics in the 3d-XY system

We investigate through Monte Carlo simulations the non-equilibrium behaviour of the threedimensional 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 λ and critical λ 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∞ is shown to vanish in the ordered phase and to reach a constant value around 0.43 for the critical quench. PACS. 75.40.Gb Dynamic properties 05.70.Ln Non-equilibrium and irreversible thermodynamics