DOI: 10.1140/epje/i2002-10075-3
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
bouchau@spec.saclay.cea.fr
(Received 15 April 2002 / Published online: 23 December 2002)
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 et al., 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
tw, quasi-exponentially at first, and then as
tw4/5 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 2002
