Off-equilibrium relaxational dynamics with an improved Ising Hamiltonian

We study the off-equilibrium relaxational dynamics at criticality in the three-dimensional Blume–Capel model whose static critical behaviour belongs to the 3D Ising universality class. Using an 'improved' Hamiltonian (the leading corrections to scaling have vanishing amplitude) we perform Monte Carlo simulations of the relaxational dynamics after a quench from T=infinity to Tc. Analysing the off-equilibrium dynamics at Tc we obtain an estimate of the dynamical critical exponent z = 2.020(8) that is perfectly consistent with the field theory predictions.