Jamming in the Gas-fluidized Bed

Statistical mechanics is one of the most complete andsuccessful theories yet devised; however, it does notdescribe non-equilibrium systems. The jamming conceptmay unify a wide class of non-equilibrium systems;however, as yet, there is little experimentalevidence to confirm or reject it. In this book are described experiments performed withgranular systems driven far from equilibrium andclose to jamming. Collections of steel ball bearingsare fluidized by turbulent air. Using high speedvideo imaging, single and collective grain dynamicsare quantified and statistical observables, such askinetic energy, diffusion coefficient, and mobility,are measured as a function of proximity to jamming.Remarkably, this non-equilibrium system behaves inquantitative analogy with equilibrium super-cooledliquids; it exhibits spatially heterogeneousdynamics: intermittent string-like clusters of fastmoving particles that evolve the system. In preciseanalogy with super-cooled liquids on approach to theglass transition, the size and lifetime of theclusters diverges on approach to the jammingtransition, providing quantitative experimentalsupport for the jamming concept.