  We study the linear response to an external perturbation of a renewal
process, in an aging condition that, with no perturbation, would yield
super-diffusion. We use the phenomenological approach to the linear response
adopted in earlier work of other groups, and we find that aging may have the
effect of annihilating any sign of coherent response to harmonic perturbation.
We also derive the linear response using dynamic arguments and we find a
coherent response, although with an intensity dying out very slowly. In the
case of a step-like perturbation the dynamic arguments yield in the long-time
limit a steady signal whose intensity may be significantly smaller than the
phenomenological approach prediction.
