Self-organized spatial inhomogeneity in self-propelled quasi-elastic hard disk systems

Graduate School of Engineering, Nagoya Institute of Technology, 466-8555, Japan.

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Published online: 12 September 2025

Abstract

The freely cooling process in inelastic hard sphere systems has been extensively studied as a fundamental model of granular gases. Here, we investigate the emergence of self-organized spatial inhomogeneities in quasielastic hard disk systems through large-scale molecular dynamics simulations. By systematically varying the packing fraction in high-density regimes near the Alder transition point, we identify novel dynamical behaviors and intriguing self-organized spatial patterns not previously reported. Additionally, we examine how different velocity scaling methods for maintaining total kinetic energy affect the system’s behavior. Our findings provide new systematic insights into self-organization phenomena in large-scale, high-density quasi-elastic hard disk systems. These results advance our understanding of collective behavior in nonequilibrium granular systems.