We obtain exact expressions for the two-time autocorrelation and response functions of the $d$-dimensional linear Glauber model. Although this linear model does not obey detailed balance in dimensions $d⩾2$, we show that the usual form of the fluctuation-dissipation ratio still holds in the stationary regime. In the transient regime, we show the occurrence of aging, with a special limit of the fluctuation-dissipation ratio, $X_{\infty }=1∕2$, for a quench at the critical point.

• Received 13 February 2006

DOI:https://doi.org/10.1103/PhysRevE.73.056117