LETTER TO THE EDITOR: On the identification of quasiprimary scaling operators in local scale-invariance

The relationship between physical observables defined in lattice models and the associated (quasi-)primary scaling operators of the underlying field theory is revisited. In the context of local scale-invariance, we argue that this relationship is only defined up to a time-dependent amplitude and derive the corresponding generalizations of predictions for two-time response and correlation functions. Applications to non-equilibrium critical dynamics of several systems, with a fully disordered initial state and vanishing initial magnetization, including the Glauber?Ising model, the Frederikson?Andersen model and the Ising spin glass are discussed. The critical contact process and the parity-conserving non-equilibrium kinetic Ising model are also considered.