论文标题
摩擦颗粒培养基中的应力相关性
Stress Correlations in Frictional Granular Media
论文作者
论文摘要
本文研究了在摩擦颗粒包装中,例如在哈密顿无定形弹性固体中,应力自相关矩阵是否会像弹性绿色的功能一样呈现远距离各向异性贡献。我们发现,在摩擦颗粒堆积的标准模型中,情况并非如此。我们通常证明,机械平衡和材料各向同性限制了应力自动相关矩阵,以通过两个空间各向同性函数完全确定:压力和扭矩自动相关。压力和扭矩波动分别是正常和超均匀的力将应力自相关作为弹性绿色功能衰减。由于我们发现扭矩波动是非常均匀的,因此罪魁祸首是其波动衰减的压力比正常的衰减速度慢于系统大小的函数。调查了这些异常压力波动的原因,我们发现在抑制稀释系统的压缩过程中已经存在异常相关性。一旦被卡住,这些相关性仍然冷冻。这是对一般摩擦物质的正确性还是模型属性的结果是一个必须等待实验性审查和可能的替代模型的问题。
This paper investigates whether in frictional granular packings, like in Hamiltonian amorphous elastic solids, the stress autocorrelation matrix presents long range anisotropic contributions just as elastic Green's functions. We find that in a standard model of frictional granular packing this is not the case. We prove quite generally that mechanical balance and material isotropy constrain the stress auto-correlation matrix to be fully determined by two spatially isotropic functions: the pressure and torque auto-correlations. The pressure and torque fluctuations being respectively normal and hyperuniform force the stress autocorrelation to decay as the elastic Green's function. Since we find the torque fluctuations to be hyper-uniform, the culprit is the pressure whose fluctuations decay slower than normally as a function of the system's size. Investigating the reason for these abnormal pressure fluctuations we discover that anomalous correlations build up already during the compression of the dilute system before jamming. Once jammed these correlations remain frozen. Whether this is true for frictional matter in general or is it the consequence of the model properties is a question that must await experimental scrutiny and possible alternative models.