Is local scale invariance a generic property of ageing phenomena ?

In contrast to recent claims by Enss, Henkel, Picone, and Schollwöck [J. Phys. A 37, 10479] it is shown by numerical simulations that the autoresponse function of the critical 1+1-dimensional contact process is not in agreement with the predictions of local scale invariance. Submitted to: Journal of Statistical Mechanics: Theory and Experiment PACS numbers: 05.50.+q, 05.70.Ln, 64.60.Ht The contact process is a simple lattice model that is often used to describe the spreading of an infectious disease [1–3]. It is defined on a hypercubic lattice whose sites can be either active or inactive. The model evolves in time by random-sequential updates in a way that each active site either spontaneously activates a nearest-neighbor site with rate λ or it becomes inactive with rate 1. Depending on the control parameter λ the (infinite) model exhibits a phase transition from a fluctuating active phase into a completely inactive absorbing state. This transition is continuous and belongs to the universality class of directed percolation (DP). Recently Enss, Henkel, Picone, and Schollwöck studied the 1+1-dimensional contact process as a generic example of ageing phenomena without detailed balance [4]. In particular, they investigated the autoresponse function R(t, s) = δ〈φ(~x, t)〉 δh(~x, s) ∣