2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/101746In glassy materials aging proceeds at large times via thermal activation. We show that this can lead to negative dynamical response functions and novel and well-defined violations of the fluctuation-dissipation theorem, in particular, negative fluctuation-dissipation ratios. Our analysis is based on detailed theoretical and numerical results for the activated aging regime of simple kinetically constrained models. The results are relevant to a variety of physical situations such as aging in glass-formers, thermally activated domain growth and granular compaction.4 pages, 4 figs; v2 final version (minor modifs) published in Phys. Rev. LettStatistical Mechanicstext