Rheology of granular media

This review is concerned with the physics of dry granular media which is the focus of many recent studies. One reason for this interest is not only due to its practical importance but also, because it is currently seen as a fundamental model with a rather broad range of applicability. The concepts and questions developed in this field have general implications in other fields such as the rheology of complex fluids (dense pastes or colloidal suspensions), the mechanics of various composite solids such as reinforced rubber, many geophysical situations and even the nano-tribology of molecular films... We review some of the aspects that were most recently discussed and which are under the scope of an intense debate.