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تسجيل مستخدم جديدStrong Dynamical Heterogeneity and Universal Scaling in Driven Granular Fluids
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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 ($varepsilon=1$) as well as inelastic ($varepsilon < 1$) collisions, are studied. As the fluid approaches structural arrest, i.e. for packing fractions in the range $0.6 le phi le 0.805$, scaling is shown to hold: $S_4(q,t)/chi_4(t)=s(qxi(t))$. Both the dynamic susceptibility, $chi_4(tau_{alpha})$, as well as the dynamic correlation length, $xi(tau_{alpha})$, evaluated at the $alpha$ relaxation time, $tau_{alpha}$, can be fitted to a power law divergence at a critical packing fraction. The measured $xi(tau_{alpha})$ widely exceeds the largest one previously observed for hard sphere 3d fluids. The number of particles in a slow cluster and the correlation length are related by a robust power law, $chi_4(tau_{alpha}) approxxi^{d-p}(tau_{alpha})$, with an exponent $d-papprox 1.6$. This scaling is remarkably independent of $varepsilon$, even though the strength of the dynamical heterogeneity increases dramatically as $varepsilon$ grows.
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