相互作用活性粒子系统中的长波不稳定性

自推进粒子有序悬浮体中的流体动力学波动和不稳定性

Hydrodynamic fluctuations and instabilities in ordered suspensions of self-propelled particles

我们构造了具有自发取向有序的自推进粒子（SPP）的{ \em悬浮液}的流体动力学方程，并作出了一些惊人的、可检验的预言：（i）具有真正{ \em悬浮液}对称性的SPP悬浮液在长波长下{ \em总是}绝对不稳定。(ii)含有{ \em极性}的SPP悬浮液，即，头-尾{ \em不对称}，阶支持长波长、耦合取向、流动和浓度下新颖传播模式。(iii)在波数制度，只有在低雷诺数系统，如细菌，极性有序悬浮液总是对流不稳定。(iv)粒子数N的方差除以平均<N>值，在极性有序SPP悬浮液中发散为$<N >^{2/3}$。

Instabilities in a self-gravitating granular gas

A kinetic and hydrodynamic descriptions are developed in order to analyze the instabilities of a granular gas in the presence of a gravitational field. In the kinetic description the Boltzmann equation is coupled with the Poisson equation, while in the hydrodynamic description the Poisson equation is coupled with the balance equations of mass density, hydrodynamic velocity and temperature for an Eulerian fluid. In the background solution for both descriptions the fluid is at rest with constant mass density and gravitational potential while the temperature depends on time through Haff's law. In…

Self-generated gradients stabilize the hydrodynamic instabilities in active suspensions

Ordered phases emerged in active suspensions of polar swimmers are under long-wavelength hydrodynamic mediated instabilities. In this letter, we show that chemical molecules dissolved in aqueous suspensions, as an unavoidable part of most wet active systems, can mediate long-range interactions and subsequently stabilize the ordered phases. Chemoattractant in living suspensions and dissolved molecules producing phoretic forces in synthesized Janus suspensions are reminiscent of such molecules. Communication between swimmers through the gradients of such chemicals generated by individual swimmer…

Oscillatory Instabilities in 3-Dimensional Frictional Granular Matter

The dynamics of amorphous granular matter with frictional interactions cannot be derived in general from a Hamiltonian and therefore displays oscillatory instabilities stemming from the onset of complex eigenvalues in the stability matrix. These instabilities were discovered in the context of one and two dimensional systems, while the three dimensional case was never studied in detail. Here we fill this gap by deriving and demonstrating the presence of oscillatory instabilities in a three dimensional granular packing. We study binary assemblies of spheres of two sizes interacting via classical…

活性膜中的非平衡涨落、行波和不稳定性

Nonequilibrium Fluctuations, Travelling Waves, and Instabilities in Active Membranes

柔性流体膜的稳定性，包含一个移动的分布，活性蛋白质（如质子泵）被证明取决于蛋白质的结构和功能不对称。稳定的活性膜处于具有高度波动的非平衡稳态，其统计特性由蛋白质活性决定。预计扰动将以足够长波长的波的形式传播，速度由泵的正常速度设定。不稳定的情况涉及膜的自发的、泵驱动的波动，在高活性区域中蛋白质聚集。

多费米子系统辅助场量子蒙特卡罗模拟中纠缠计算的数值稳定性

Numerical stabilization of entanglement computation in auxiliary field quantum Monte Carlo simulations of interacting many-fermion systems

在没有费米子符号问题的情况下，辅助场（或行列式）量子蒙特卡罗（DQMC）方法长期以来一直是无偏的，相互作用的多费米子系统的大规模模拟的数值方法的选择。最近，这种方法的概念范围已经扩大，通过引入巧妙的计划来计算纠缠熵在其框架内。然而，在实践层面上，这些方法存在各种数值不稳定性，这在很大程度上阻碍了它们的适用性。在这里，我们报告了一些算法的进步，以克服许多这些数值不稳定性，并显着提高计算的纠缠措施在零温度投影DQMC方法，最终允许达到类似的系统大小为传统的可观的计算。我们证明了这种改进的DQMC方法的适用性，通过提供一个纠缠的角度来看，从磁有序的莫特绝缘体带绝缘体的双层正方形晶格哈伯德模型在半填充的量子相变。