AI 中文总结
研究被动和主动丝状极性流体系统中的相排序与缺陷动力学，通过新单场模型数值模拟，揭示两种排列相互作用下的缺陷机制、动态标度等，还发现活性导致的现象，为理解该类系统提供统一框架。
AI 中文摘要
在广泛的生物和合成活性系统中观察到的极性和向列相互作用的共存，产生了丰富的现象学，持续挑战我们对非平衡集体行为的理论理解。本文通过数值研究了一种新引入的用于干燥丝状极性流体系统的最小单场模型中的相排序和缺陷动力学。在两种排列的最佳平衡下，系统会形成连接半整数缺陷并分隔相反极化区域的去极化弦以及闭合的去极化环。首先表征了缺陷对和环的基本弛豫机制，表明极性和向列排列之间的相互作用产生了非单调的弦介导相互作用、有限的平衡间距和不同的环坍缩路径。从无序状态进行的大规模模拟显示动态标度，特征长度以$\sim(t/\ln t)^{1/2}$增长，与具有非守恒序参量和点状缺陷的系统中的粗化一致。引入自平流后，足够强的活性导致正整数和负半整数缺陷共存，即运动诱导电荷对称性破缺，并使特征长度尺度饱和，最终导致粗化停滞。总体而言，我们的结果为理解生物和合成丝状极性流体系统中的排序和缺陷动力学提供了一个简单统一的框架。
英文摘要
The coexistence of polar and nematic interactions, observed in a broad range of biological and synthetic active systems, gives rise to a rich phenomenology that continues to challenge our theoretical understanding of non-equilibrium collective behaviour. In this paper, we numerically investigate phase ordering and defect dynamics in a newly introduced minimal single-field model for dry nematopolar systems, where competing polar and nematic contributions enter the free energy, and activity is implemented through self-advection. At optimal balance, the system develops depolarization strings connecting half-integer defects and separating domains with opposite polarization, together with closed depolarization loops. We first characterize the elementary relaxation mechanisms of defect pairs and loops, showing that the interplay between polar and nematic alignment gives rise to non-monotonic string-mediated interactions, finite equilibrium separations and distinct loop-collapse pathways. Large-scale simulations from disordered states instead show dynamic scaling with a characteristic length growing as $\sim(t/\ln t)^{1/2}$, consistent with coarsening in systems with non-conserved order parameters and point-like defects. Upon introducing self-advection, sufficiently strong activity leads to the coexistence of positive integer and negative half-integer defects, which we term motility-induced charge symmetry breaking, and to saturation of the characteristic length scales, ultimately resulting in arrested coarsening. Overall, our results provide a simple unified framework for understanding the ordering and defect dynamics in biological and synthetic nematopolar systems.
Comments17 pages, 6 figures
