Brey J Javier, García de Soria M I, Maynar P, Ruiz-Montero M J
Física Teórica, Universidad de Sevilla, Apdo. de Correos 1065, E-41080 Sevilla, Spain.
Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Jul;70(1 Pt 1):011302. doi: 10.1103/PhysRevE.70.011302. Epub 2004 Jul 29.
Starting from the hierarchy of equations for microscopic densities in phase space, a general theory for fluctuations and correlations in a dilute granular gas of hard particles is developed. Then, the particular case of the homogeneous cooling state is addressed. Explicit expressions for some distributions describing the presence of velocity correlations and their dynamics are obtained. These correlations are inherent to the dissipative dynamics of the collisions. The implications for the behavior of the total energy of the system are analyzed and the results are expressed in terms of a fluctuation-dissipation theorem. The theoretical predictions are shown to be in agreement with results obtained by molecular dynamics simulations, which also indicate that energy fluctuations are well described by a Gaussian distribution.
从相空间中微观密度的方程层次出发，发展了一种关于硬颗粒稀薄颗粒气体中涨落和关联的一般理论。然后，研究了均匀冷却态的特殊情况。得到了一些描述速度关联及其动力学的分布的显式表达式。这些关联是碰撞耗散动力学所固有的。分析了对系统总能量行为的影响，并根据涨落耗散定理给出了结果。理论预测结果与分子动力学模拟结果一致，分子动力学模拟结果还表明能量涨落可用高斯分布很好地描述。
