Granular materials (e.g. sand, powders, concrete, seeds, pills and so on) are subject to a recent strong scientific interest: they are materials of fundamental importance for industry and agriculture. The economic impact of a better comprehension of their collective properties has been estimated to be of the order of the billions of dollars per year.
The physics of granular materials has unveiled a large number of intriguing phenomena: granular systems can behave like gases, liquids or solids, depending on boundary conditions and intensity of the external driving. However, in all these three "states", a granular system displays always specific and anomalous properties. In particular, dilute granular systems, fluidized by means of an external energy input, due to the non-conservative characters of their interaction, "violate" several fundamental principles of statistical physics, such as the second principle of thermodynamics, the equipartition of energy or the Maxwell-Boltzmann statistics.
Packed granular systems (for example a buckle full of sand, tapped from the bottom) surprisingly reveal strong analogies with glassy systems (spin glass or structural glasses), showing disorder, frustration and very slow relaxation processes. In a word, a granular system, from the point of view of physics, is the perfect case study for modern non-equilibrium statistical mechanics. At the same time, a full understanding of granular systems can have real consequences in industrial and technological applications.
The specific objective of this project is to join the two mainstreams of granular physics, that is, dense solid-like and dilute fluid-like granulars, investigating the transition between those two phases when external parameters (such as the intensity of the shaking or the global packing fraction) are properly changed.
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