Eur. Phys. J. E 6, 231-236 (2001)
Anomalous dynamical light scattering in soft glassy gelsJ.-P. Bouchaud1 and E. Pitard2
1 Service de Physique de l'État Condensé, Centre d'études de Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France
2 Laboratoire de Physique Mathématique et Théorique, Université Montpellier II, UMR 5825, France
(Received 23 July 2001)
We compute the dynamical structure factor of an elastic medium where force dipoles appear at random in space and in time, due to "micro-collapses" of the structure. Various regimes are found, depending on the wave vector q and the collapse time . In an early-time regime, the logarithm of the structure factor behaves as , as predicted in L. Cipelletti, S. Manley, R.C. Ball, D.A. Weitz, Phys. Rev. Lett. 84, 2275 (2000) using heuristic arguments. However, in an intermediate-time regime we rather obtain a behaviour. Finally, the asymptotic long-time regime is found to behave as . We also give a plausible scenario for aging, in terms of a strain-dependent energy barrier for micro-collapses. The relaxation time is found to grow with the age , quasi-exponentially at first, and then as with logarithmic corrections.
82.70.Gg - Gels and sols.
81.40.Cd - Solid solution hardening, precipitation hardening, and dispersion hardening; aging.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001