title: Strong dynamical heterogeneity and universal scaling in driven granular fluids.
abstract: Large-scale simulations of two-dimensional bidisperse granular fluids allow us to determine spatial correlations of slow particles via the four-point structure factor S(4)(q,t). Both cases, elastic (ϵ=1) and inelastic (ϵ<1) collisions, are studied. As the fluid approaches structural arrest, i.e., for packing fractions in the range 0.6≤ϕ≤0.805, scaling is shown to hold: S(4)(q,t)/χ(4)(t)=s(qξ(t)). Both the dynamic susceptibility χ(4)(τ(α)) and the dynamic correlation length ξ(τ(α)) evaluated at the α relaxation time τ(α) can be fitted to a power law divergence at a critical packing fraction. The measured ξ(τ(α)) widely exceeds the largest one previously observed for three-dimensional (3d) hard sphere fluids. The number of particles in a slow cluster and the correlation length are related by a robust power law, χ(4)(τ(α))≈ξ(d-p)(τ(α)), with an exponent d-p≈1.6. This scaling is remarkably independent of ϵ, even though the strength of the dynamical heterogeneity at constant volume fraction depends strongly on ϵ.
authors: Department of Physics and Astronomy and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701, USA and Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 17, D-37077 Göttingen, Germany.
authors: Karina E
authors: KE
authors: Avila
authors: Department of Physics and Astronomy and Nanoscale and Quantum Phenomena Institute, Ohio University, Athens, Ohio 45701, USA.
authors: Horacio E
authors: HE
authors: Castillo
authors: Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.
authors: Andrea
authors: A
authors: Fiege
authors: Department of Physics and Astronomy, Bucknell University, Lewisburg, Pennsylvania 17837, USA.
authors: Katharina
authors: K
authors: Vollmayr-Lee
authors: Max-Planck-Institut für Dynamik und Selbstorganisation, Am Fassberg 17, D-37077 Göttingen, Germany and Institut für Theoretische Physik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.
authors: Annette
authors: A
authors: Zippelius