arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1509.03395cond-mat.stat-mechcond-mat.softphysics.bio-ph
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群集模型中的斑图形成:流体动力学描述

Pattern formation in flocking models: A hydrodynamic description

Alexandre P. Solon, Jean-Baptiste Caussin, Denis Bartolo, Hugues Chaté, Julien Tailleur

摘要:

我们详细研究了描述极性活性物质向集体运动过渡的流体动力学理论,以Vicsek和活性伊辛模型为例。使用一个简单的唯象理论,我们证明了存在一个无限的传播的解决方案,描述相和微相分离,我们充分的特点。我们还表明,同样的结果持有具体的流体动力学方程在文献中推导出的主动伊辛模型和简化版本的Vicsek模型。然后,我们数值研究这些解决方案的线性稳定性。我们表明,稳定的只占其中的一小部分,但包括所有现有的类型。我们进一步认为,在实践中,粗化机制导致相分离的解决方案。最后,我们构建的流体动力学方程的相图提出定性描述Vicsek和积极的伊辛模型和连接我们的结果相应的微观模型的现象。

英文摘要:

We study in detail the hydrodynamic theories describing the transition to collective motion in polar active matter, exemplified by the Vicsek and active Ising models. Using a simple phenomenological theory, we show the existence of an infinity of propagative solutions, describing both phase and microphase separation, that we fully characterize. We also show that the same results hold specifically in the hydrodynamic equations derived in the literature for the active Ising model and for a simplified version of the Vicsek model. We then study numerically the linear stability of these solutions. We show that stable ones constitute only a small fraction of them, which however includes all existing types. We further argue that in practice, a coarsening mechanism leads towards phase-separated solutions. Finally, we construct the phase diagrams of the hydrodynamic equations proposed to qualitatively describe the Vicsek and active Ising models and connect our results to the phenomenology of the corresponding microscopic models.

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