We investigate numerically the dynamics of three different spin models in the
aging regime. Each of these models is meant to be representative of a distinct
class of aging behavior: coarsening systems, discontinuous spin glasses, and
continuous spin glasses. In order to study dynamic heterogeneities induced by
quenched disorder, we consider single-spin observables for a given disorder
realization. In some simple cases we are able to provide analytical predictions
for single-spin response and correlation functions.
The results strongly depend upon the model considered. It turns out that, by
comparing the slow evolution of a few different degrees of freedom, one can
distinguish between different dynamic classes. As a conclusion we present the
general properties which can be induced from our results, and discuss their
relation with thermometric arguments.Comment: 39 pages, 36 figure