Sub-aging in a Domain Growth Model

We study analytically the aging dynamics of the O(n) model in the large-n limit, with conserved and with non-conserved order parameter. While in the non-conserved dynamics, the autocorrelation function scales in the usual way C(t,tw) = C(t/tw), in the case of a conserved order parameter, `multiscaling' manifests itself in the form C(t,tw) = C (h(t)/h(tw)), with a relaxation time growing more slowly than the age of the system (sub-aging), and h(t) a function growing faster than any length scale of the problem. In both cases, the effective temperature associated to the violation of the fluctuation theorem tends to infinity in the asymptotic limit of large waiting times

A few bubbles in a glass

I briefly review a recent series of papers putting forward a coarse-grained theoretical approach to the physics of supercooled liquids approaching their glass transition. After a suitable coarse-graining, the dynamics of the liquid is replaced by that of a mobility field, which can then be analytically treated. The statistical properties of the mobility field then determine those of the liquid. Thermodynamic, spatial, topographic, dynamic properties of the liquid can then be quantitatively described within a single framework, and derive from the existence of an underlying dynamic critical point located at zero-temperature, where timescales and lengthscales diverge.Comment: Paper presented at "Fluctuations and Noise 2004", May 25-28, 2004, Maspalomas, Gran Canaria, Spai

Dynamic heterogeneity in amorphous materials

Amorphous solids are mechanically rigid while possessing a disordered structure similar to that of dense liquids. Recent research indicates that dynamical heterogeneity, spatio-temporal fluctuations in local dynamical behavior, might help understanding the statistical mechanics of glassy states.Comment: 7 pages; 5 figures -- "Trends" article published by Physics at http://physics.aps.org/articles/v4/4

Nonequilibrium glass transitions in driven and active matter

The glass transition, extensively studied in dense fluids, polymers, or colloids, corresponds to a dramatic evolution of equilibrium transport coefficients upon a modest change of control parameter, like temperature or pressure. A similar phenomenology is found in many systems evolving far from equilibrium, such as driven granular media, active and living matter. While many theories compete to describe the glass transition at thermal equilibrium, very little is understood far from equilibrium. Here, we solve the dynamics of a specific, yet representative, class of glass models in the presence of nonthermal driving forces and energy dissipation, and show that a dynamic arrest can take place in these nonequilibrium conditions. While the location of the transition depends on the specifics of the driving mechanisms, important features of the glassy dynamics are insensitive to details, suggesting that an `effective' thermal dynamics generically emerges at long time scales in nonequilibrium systems close to dynamic arrest.Comment: 7 pages, 2 fig