谐振子链中的主动涨落：声子、熵子与速度关联
Active fluctuations in the harmonic chain: phonons, entropons and velocity correlations
AI总结：
本文研究一维活性谐振子链的集体激发，发现声子与熵子两类涨落，推导了速度、位移关联及结构因子的精确表达式，并揭示了二者在过阻尼与欠阻尼区的动力学差异及活性对振荡的抑制作用。
摘要：
非热性质的平衡态随机涨落是活性物质的一个显著特征。本文考虑高密度下活性系统的集体激发，聚焦于一维弹性耦合惯性粒子链，其活性由Ornstein-Uhlenbeck过程建模。其激发谱显示存在两类涨落：第一类是被动晶体中类似的热激发声子，第二类被称为熵子（entropons），因为它们与活性力引起的熵产生相关。这两类涨落表现出不同的性质：事实上，只有熵子产生空间速度关联，并且不满足标准的涨落-响应关系。我们推导了等时速度关联、位移关联以及结构因子的精确表达式，并在每种情况下识别出声子和熵子的贡献。最后，我们通过稳态双时关联（如中间散射函数和均方位移）研究激发的动力学性质，并表明声子和熵子涨落均具有长波过阻尼区和短波欠阻尼区的特征。在大持久性情况下，熵子比声子衰减更慢，并且总体而言，活性倾向于抑制欠阻尼区典型的振荡。
英文摘要：
Non-equilibrium random fluctuations of non-thermal nature are a salient feature of active matter. In this work, we consider the collective excitations of active systems at high density, focusing on a one-dimensional chain of elastically coupled inertial particles, whose activity is modeled with an Ornstein-Uhlenbeck process. Their excitation spectrum shows the presence of two kinds of fluctuations: the first ones are thermally excited phonons analogous to those of a passive crystal while the second ones have been termed entropons because associated with the entropy production due to the active forces. These two types of fluctuations show different properties: in fact, only entropons generate spatial velocity correlations and fail to satisfy a standard fluctuation-response relation. We derive the exact expression for the equal-time velocity and displacement correlations as well as for the structure factor and in each case identify the phonon and entropon contributions. Finally, we investigate the dynamical properties of the excitations in terms of steady-state two-time correlations, such as the intermediate scattering function and the mean-square displacement, and show that both phonon and entropon fluctuations are characterized by a long wavelength overdamped regime and a short wavelength underdamped regime. In the large persistence case, entropons decay slower than phonons, and in general, activity tends to suppress the oscillations typical of the underdamped regime.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
