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arXiv 2412.04450cond-mat.softcond-mat.stat-mech
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运动诱导相分离晶格模型中的界面与密度涨落

Interfacial and density fluctuations in a lattice model of motility-induced phase separation

Liheng Yao, Robert L. Jack

AI总结:

本文通过二维自推进粒子晶格模型研究运动诱导相分离,比较平板与液滴构型,揭示气泡与界面的时间尺度分离及曲率相关的密度涨落规律。

摘要:

我们分析了一个二维自推进粒子晶格模型中的运动诱导相分离和气泡相分离。我们比较了稠密(液体)相具有平板和液滴几何构型的系统。我们发现,尽管稠密相中存在气泡,平板的界面涨落仍可由毛细波理论很好地描述。我们将此归因于气泡排出与界面弛豫之间的时间尺度分离。我们还表征了液体和蒸气密度对液滴曲率的依赖关系,以及各相内部的密度涨落。气相的行为类似于平衡系统,表现出使其密度发生偏移的拉普拉斯压力效应,以及高斯密度涨落。液相具有较大的非高斯涨落,但与平衡情形相反,这并未伴随较大的密度偏移。尽管如此,气相密度的偏移仍可用于推断有效表面张力,而该张力似乎也能定量描述毛细波涨落。

英文摘要:

We analyze motility-induced phase separation and bubbly phase separation in a two-dimensional lattice model of self-propelled particles. We compare systems where the dense (liquid) phase has slab and droplet geometries. We find that interfacial fluctuations of the slab are well-described by capillary wave theory, despite the existence of bubbles in the dense phase. We attribute this to a separation of time scales between bubble expulsion and interfacial relaxation. We also characterize dependence of liquid and vapor densities on the curvature of the liquid droplet, as well as the density fluctuations inside the phases. The vapor phase behaves similarly to an equilibrium system, displaying a Laplace pressure effect that shifts its density, and Gaussian density fluctuations. The liquid phase has large non-Gaussian fluctuations, but this is not accompanied by a large density shift, contrary to the equilibrium case. Nevertheless, the shift of the vapor density can be used to infer an effective surface tension that appears to also quantify capillary wave fluctuations.

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