  We investigate violations of the fluctuation-dissipation theorem in two
classes of trap models by studying the influence of the perturbing field on the
transition rates. We show that for perturbed rates depending upon the value of
the observable at the arrival trap, a limiting value of the
fluctuation-dissipation ratio does exist. However, the mechanism behind the
emergence of this value is different in both classes of models. In particular,
for an entropically governed dynamics (where the perturbing field shifts the
relative population of traps according to the value of the observable)
perturbed rates are argued to take a form that guarantees the existence of a
limiting value for the effective temperature, utterly related to the
exponential character of the distribution of trap energies.
Fluctuation-dissipation (FD) plots reproduce some of the patterns found in a
broad class of glassy systems, reinforcing the idea that structural glasses
self-generate a dynamical measure that is captured by phenomenological trap
models.
