Acoustical waves propagating along the free surface of granular media under gravity are investigated in the framework of elasticity theory. The influence of stress on a surface wave is analyzed. The results have shown that two types of surface waves, namely sagittal and transverse modes exist depending on initial stress states, which may have some influence on the dispersion relations of surface waves, but the influence is not great. Considering that the present experimental accuracy is far from distinguishing this detail, the validity of elasticity theory on the surface waves propagating in granular media can still be maintained.
运用有限系统密度矩阵重整化群算法(FS-DMRG),研究拓展Bose-Hubbard模型(即在标准BoseHubbard模型的基础上加入最近邻格点间的粒子相互排斥作用V)发生相变的特征。通过计算系统的局域粒子数密度、单粒子能隙以及压缩系数,分析了系统在不同状态下的特征,得到了不同于标准Bose-Hubbard模型的新量子态——Charge Density Wave(CDW)态。通过分析产生特殊粒子分布方式的原因及其物理性质,得出了发生相变的临界条件。
