Some comment on “The glass-Jamming transition in dense granular matter”, by C. Coulais, R. Candelier & O. Dauchot, a lecture at Powders & Grains 2013

P. Evesque, 92290 Châtenay-Malabry, France , pierre.evesque@ecp.fr :

Abstract :

A large number of works has been devoted to the study of large “non classic” fluctuations expected in the physics and mechanics of granular matter. This topics was developed after the introduction of the “Jamming” and “fragility” concepts as unifying modelling for glass-gels-and-granular materials in 1998. To the point of view of the above lecturers, this was a success. To the point of view f the commentator, this success is not real, since the concept of “jamming & fragility” splits into different problems as soon it is applied to separate real problem (glass transition, dense static flow of granular matter, jamming in gels jamming in frictionless grain matter,…, each one looking at some kind of phase transition. However, theory of phase transition has to relate different real phases, so they can be grouped into different class of some real classification (as 1st order or 2nd order phase transition), and split in subsection (which may depend on interaction dimensionality and space dimensionality as in 2nd order phase transition). On the contrary, when applied to granular matter problem, one can define many different bifurcations, which depend on the granular matter characteristics and the “flow”, so that we do not know if the classification should be finite or infinite.

Pacs # : 5.40 ; 45.70 ; 62.20 ; 83.70.Fn ; 45.35i ; 45.70.Mg; 83.80.fg ; 46.80.Ff ; 05.20.-y

poudres & grains 21, 20-24 ( Juin 2013)