  We study analytically the aging dynamics of the O(n) model in the large-n
limit, with conserved and with non-conserved order parameter. While in the
non-conserved dynamics, the autocorrelation function scales in the usual way
C(t,tw) = C(t/tw), in the case of a conserved order parameter, `multiscaling'
manifests itself in the form C(t,tw) = C (h(t)/h(tw)), with a relaxation time
growing more slowly than the age of the system (sub-aging), and h(t) a function
growing faster than any length scale of the problem. In both cases, the
effective temperature associated to the violation of the fluctuation theorem
tends to infinity in the asymptotic limit of large waiting times.
