Eur. Phys. J. E 6, 231-236 (2001)
Anomalous dynamical light scattering in soft glassy gels
J.-P. Bouchaud1 and E. Pitard21 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
boucheau@spec.saclay.cea.fr
estelle@lpm.univ-montp2.fr
(Received 23 July 2001)
Abstract
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
