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The dynamics in granular matter is inherently out-of-equilibrium, as time-reversal symmetry is broken by the energy loss during interparticle collisions. This presents challenges to both theory and experiment: Experimentally, granular systems need to be agitated strongly to achieve steady states or need to be measured in microgravity to avoid sedimentation. For the theoretical treatment, suitable ensembles need to be assumed or inferred from experiments. Experiments from parabolic-flight and drop-tower campaigns shall be shown for the dilute regime of granular gases where homogeneous steady states and granular cooling are observed. For dense granular fluids, the derivation of granular rheology from first principles shall be presented as well as new experimental techniques for the characterization of granular states such as X-ray radiography and tomography, and terahertz scattering.

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Dr. Matthias Sperl, DLR Cologne
Seminarraum Theoretische Physik
Contact: Joachim Krug