WYART GROUP


Photos: (1) Force chains appear in photo-elastic particles, Berhinger lab.  (2) Soft mode in a  packing of discs. (3) The nematode C.elegans, J. Berger.

Photos: (1) Force chains appear in photo-elastic particles, Berhinger lab.
(2) Soft mode in a packing of discs. (3) The nematode C.elegans, J. Berger.






Glassy materials are currently the main focus of our group. These systems are so slow that they fall out-of-equilibrium. Their physical properties thus depend on their history, implying that they display some kind of memory. We seek principles replacing thermodynamics to describe the ensemble of configurations visited in this systems- a necessary condition to describe the glassy phase at low temperature or drive. We focus on amorphous solids, arguably the simplest example of glassy materials, such as sand or glasses. Recently we have shown for packing of hard particles that these configurations are those for which small perturbation can have large effects, in some way similar to ideas used in dirty semi-conductors in the 70’s. Another intriguing, poorly understood property of glassy materials is the transition they display between a fluid and a jammed phase. When amorphous solids are sheared the dynamic is reminiscent of a critical point, with a diverging length scale signaling that the dynamics is more and more collective as the solid phase is approached. We seek to describe flow near the jamming transition as a perturbation around the solid phase, where recent progress has been made.



Another interest is the quantitative characterization and modeling of behaviors, ranging from C. Elegans with its 302 neurons to financial markets where a plethora of data is available.