Strong dynamical heterogeneity and universal scaling in driven granular fluids

Area of Science:

• Physics
• Soft Matter Physics
• Computational Physics

Background:

• Granular materials exhibit complex dynamics, including dynamical heterogeneity.
• Understanding particle correlations is crucial for predicting material behavior near jamming.
• Previous studies often focused on simpler systems or lacked detailed correlation analysis.

Purpose of the Study:

• To investigate spatial correlations of slow particles in 2D bidisperse granular fluids.
• To determine the scaling behavior of the four-point structure factor near structural arrest.
• To compare elastic and inelastic collision effects on these correlations.

Main Methods:

• Large-scale simulations of 2D bidisperse granular fluids.
• Analysis of the four-point structure factor, S(4)(q,t).
• Evaluation of dynamic susceptibility (χ(4)) and dynamic correlation length (ξ) at the α relaxation time (τ(α)).

Main Results:

• Observed scaling S(4)(q,t)/χ(4)(t)=s(qξ(t)) in the range 0.6≤ϕ≤0.805.
• Demonstrated power-law divergence of χ(4) and ξ at a critical packing fraction.
• Found ξ significantly larger than in 3D hard sphere fluids.
• Established a robust power-law relation: χ(4)(τ(α))≈ξ(d-p)(τ(α)) with d-p≈1.6.

Conclusions:

• Granular fluids near structural arrest exhibit universal scaling behavior for slow particle correlations.
• The observed scaling is remarkably independent of the collision elasticity (ϵ).
• The findings provide insights into the nature of dynamical heterogeneity in dense granular systems.