1202.5687 (C. Coulais et al.)

Contacts Dynamics across Jamming in a granular glass experiment    [PDF]

C. Coulais, R. P. Behringer, O. Dauchot

We study experimentally the vicinity of the Jamming transition by investigating the statics and the dynamics of the contact network of an horizontally shaken bi-disperse packing of photo-elastic discs. Compressing the packing very slowly, while maintaining a mechanical excitation, we produce a granular glass, namely a frozen structure of vibrating grains. Nevertheless, we observe in this glass phase a remarkable dynamics of the contact network, which exhibits strong dynamical hetero-geneities. Such heterogeneities are maximum at a packing fraction {\phi}\star, distinct and smaller than the jamming packing fraction {\phi}_{J}, which is indicated by the abrupt variation of the average number of contact per particle. We further demonstrate that the "dynamical transition" taking place at {\phi}\star originates in the spatial correlation of the coordination number. Our findings are discussed in the light of recent numerical and theoretical studies of thermal soft spheres.

View original: http://arxiv.org/abs/1202.5687