A Simple Model for Simple Aging in Glassy Yttrium-Hydrides
  A simple explanation for the logarithmic aging of the photoconductivity in yttriumhydride is proposed. We show that the scaling (``simple'' aging) of the relaxation response with the illumination time t_w is consistent with the superposition of independently relaxing excitations with time offsets distributed over a window of width t_w. 
M. Mueller