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arXiv 2302.04259cond-mat.soft
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三维活性极性流体中的自发流动不稳定性

Spontaneous flow instabilities of active polar fluids in three dimensions

Abhinav Singh, Quentin Vagne, Frank Jülicher, Ivo F. Sbalzarini

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AI总结：

本研究通过三维活性埃里克森-莱斯利模型，揭示了边界条件如何选择活性极性流体的自发流动不稳定性模式，并解释了面内与面外失稳的机制。

摘要：

活性极性流体在内部分子机制产生足够大的活性应力时会表现出自发流动，这被称为活性弗莱德里克斯转变。实验已经揭示了三维活性物质中存在面内和面外不稳定性之间的竞争。然而，迄今为止，尚未有一个理论模型能够调和所有观测结果。特别是，边界条件在这些不稳定性中的作用仍有待解释。在此，我们在一个保持对称性的三维活性埃里克森-莱斯利模型中表征了自发流动转变，表明边界条件决定了涌现行为。通过非线性数值解和线性扰动分析，我们解释了在垂直极性锚定边界条件下，伸展型活性应力导致面内和面外不稳定性的机制；而平行锚定仅在收缩应力下允许面内流动，或在伸展应力下允许面外皱褶。

英文摘要：

Active polar fluids exhibit spontaneous flow when sufficient active stress is generated by internal molecular mechanisms. This is also referred to as an active Fréedericksz transition. Experiments have revealed the existence of competing in-plane and out-of-plane instabilities in three-dimensional active matter. So far, however, a theoretical model reconciling all observations is missing. In particular, the role of boundary conditions in these instabilities still needs to be explained. Here, we characterize the spontaneous flow transition in a symmetry-preserving three-dimensional active Ericksen-Leslie model, showing that the boundary conditions select the emergent behavior. Using nonlinear numerical solutions and linear perturbation analysis, we explain the mechanism for both in-plane and out-of-plane instabilities under extensile active stress for perpendicular polarity anchoring at the boundary, whereas parallel anchoring only permits in-plane flows under contractile stress or out-of-plane wrinkling under extensile stress.

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