Aging in models of nonlinear diffusion

We show that for a class of problems described by the nonlinear diffusion equation partial derivative/partial derivative t phi(mu) = D partial derivative(2)/partial derivative x(2) phi(nu) an exact calculation of the two time autocorrelation function gives C(t,t') = f(t-t')g(t') (t>t') exhibiting normal and anomalous diffusions, as well as aging effects, depending on the values of mu and nu. We also discuss the form in which the Fluctuation-dissipation theorem is violated in this type of systems. Finally, we argue that in this kind of model, aging may be a consequence of the nonconservation of the ''total mass''.