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Statistical Theory Of Correlations In Random Packings Of Hard Particles, Yuliang Jin, James G. Puckett, Hernán A. Makse
Statistical Theory Of Correlations In Random Packings Of Hard Particles, Yuliang Jin, James G. Puckett, Hernán A. Makse
Physics and Astronomy Faculty Publications
A random packing of hard particles represents a fundamental model for granular matter. Despite its importance, analytical modeling of random packings remains difficult due to the existence of strong correlations which preclude the development of a simple theory. Here, we take inspiration from liquid theories for the n-particle angular correlation function to develop a formalism of random packings of hard particles from the bottom up. A progressive expansion into a shell of particles converges in the large layer limit under a Kirkwood-like approximation of higher-order correlations. We apply the formalism to hard disks and predict the density of two-dimensional random …
Searching For Effective Forces In Laboratory Insect Swarms, James G. Puckett, Douglas H. Kelley, Nicholas T. Ouellette
Searching For Effective Forces In Laboratory Insect Swarms, James G. Puckett, Douglas H. Kelley, Nicholas T. Ouellette
Physics and Astronomy Faculty Publications
Collective animal behaviour is often modeled by systems of agents that interact via effective social forces, including short-range repulsion and long-range attraction. We search for evidence of such effective forces by studying laboratory swarms of the flying midge Chironomus riparius. Using multi-camera stereoimaging and particle-tracking techniques, we record three-dimensional trajectories for all the individuals in the swarm. Acceleration measurements show a clear short-range repulsion, which we confirm by considering the spatial statistics of the midges, but no conclusive long-range interactions. Measurements of the mean free path of the insects also suggest that individuals are on average very weakly coupled, but …