Origin of the slow dynamics and the aging of a soft glass
  We study by light microscopy a soft glass consisting of a compact arrangement of polydisperse elastic spheres. We show that its slow and non-stationary dynamics results from the unavoidable small fluctuations of temperature, which induce intermittent local mechanical shear in the sample, because of thermal expansion and contraction. Temperature-induced shear provokes both reversible and irreversible rearrangements whose amplitude decreases with time, leading to an exponential slowing down of the dynamics with sample age. 
Sylvain Mazoyer (LCVN), Luca Cipelletti (LCVN), Laurence Ramos (LCVN)