标题： 二维手性马尔萨斯群集的水动力学理论 显示英文标题

标题： Hydrodynamic Theory of Two-dimensional Chiral Malthusian Flocks

摘要： 我们研究二维手性干马尔萨斯 flock 的流体力学行为；即，既没有粒子数也没有动量守恒的手性极性有序活性物质。 我们表明，在没有涨落的情况下，这样的系统通常会形成一个“时间胆甾”，其中整个系统的速度以固定的频率 b 均匀旋转。 对该状态的涨落属于 (2+1)-Kardar-Parisi-Zhang (KPZ) 方程的普适类，这意味着在流体力学极限下具有短程取向序。 然后我们表明，在弱手性极限下，具有合理尺寸的系统的流体力学预期由 KPZ 方程的线性区域主导，表现出准长程取向序。 我们对速度和粒子数密度关联的预测可在模拟和实验中进行验证。 显示英文摘要

摘要： We study the hydrodynamic behavior of two-dimensional chiral dry Malthusian flocks; that is, chiral polar-ordered active matter with neither number nor momentum conservation. We show that, in the absence of fluctuations, such systems generically form a ``time cholesteric", in which the velocity of the entire system rotates uniformly at a fixed frequency b. Fluctuations about this state belong to the universality class of (2+1)-Kardar-Parisi-Zhang (KPZ) equation, which implies short-ranged orientational order in the hydrodynamic limit. We then show that, in the limit of weak chirality, the hydrodynamics of a system with reasonable size is expected to governed by the linear regime of the KPZ equation, exhibiting quasi-long-ranged orientational order. Our predictions for the velocity and number density correlations are testable in both simulations and experiments.