La transition de "Jamming" dans un milieu granulaire bidimensionnel : Statique et dynamique d'un système athermique modèle

Abstract : The Jamming transition is a generic phenomenon that occurs when an assembly abruptly ceases to evolve. This thesis proposes a characterization of the statistical properties of a model athermal system in the vicinity of this transition. The system, a bidimensionnal layer of 8500 metal cylinders, is studied in two experimental situations. The first one consists in examining the interstitial volume trapped in vertical packings of these grains. We show that in this static situation, the system exhibits long range correlations and a lack of extensivity. The second situation consists in vibrating such an assembly in the horizontal plane at various densities.We identify the Jamming transition on the force signal at the boundary.We study the diffusion properties together with the density field relaxation, and show that they both are governed by the same length scale.We then study the spatial heterogeneity of the dynamics by means of a four-point correlation function, which is found to verify critical scaling. The correlation length and a relaxation time scale associated with marginal super diffusion are maximum across the transition. We conclude that Jamming is a dynamical phase transition that nevertheless differs from the glass transition. Finally, our system is found to saturate a fluctuation dissipation inequality, which shows that the amplitude of spontaneous fluctuations of the dynamics is reproduced by its response to a change in density. We conclude that the latter governs the macroscopic properties of the system.
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Contributor : Frederic Lechenault <>
Submitted on : Friday, December 21, 2007 - 6:35:52 PM
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Frederic Lechenault. La transition de "Jamming" dans un milieu granulaire bidimensionnel : Statique et dynamique d'un système athermique modèle. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université Paris Sud - Paris XI, 2007. Français. ⟨tel-00200902⟩

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