标题： 液-气不对称性和波矢依赖的表面张力 显示英文标题

标题： Liquid-Gas Asymmetry and the Wavevector-Dependent Surface Tension

摘要： 尝试通过引入有效波矢（$q$）依赖的表面张力（$\sigma_\text{eff}(q)$）将毛细波理论扩展到微观波长，遇到了困难。 对于$\sigma_\text{eff}(q)$的形状尚无一致意见。 通过对液气界面的简单密度泛函模型进行分析，我们确定了将微观可观测量分为背景和界面贡献的不同方案。 为了使密度-密度相关函数和局部结构因子的背景在加权体相气体和液体贡献的术语中具有一致且物理上有意义的解释，总结构因子的背景必须由一个之前未被识别的微观$q$-依赖长度$\zeta(q)$来表征。 在我们的模型中，明确展示了包括$q$对$\zeta(q)$的依赖性的必要性，并具有更广泛的意义，即 在典型的实验和模拟研究中，$\zeta(q)$的不确定性始终存在，这让人联想到毛细波理论中使用的截断。 这不可避免地导致$q$对$\sigma_\text{eff}(q)$的依赖关系存在较大的不确定性。 显示英文摘要

摘要： Attempts to extend the capillary-wave theory of fluid interfacial fluctuations to microscopic wavelengths, by introducing an effective wave-vector ($q$) dependent surface tension $\sigma_\text{eff}(q)$, have encountered difficulties. There is no consensus as to even the shape of $\sigma_\text{eff}(q)$. By analysing a simple density functional model of the liquid-gas interface, we identify different schemes for separating microscopic observables into background and interfacial contributions. In order for the backgrounds of the density-density correlation function and local structure factor to have a consistent and physically meaningful interpretation in terms of weighted bulk gas and liquid contributions, the background of the total structure factor must be characterised by a microscopic $q$-dependent length $\zeta(q)$ not identified previously. The necessity of including the $q$ dependence of $\zeta(q)$ is illustrated explicitly in our model and has wider implications, i.e. in typical experimental and simulation studies, an indeterminacy in $\zeta(q)$ will always be present, reminiscent of the cut-off used in capillary-wave theory. This leads inevitably to a large uncertainty in the $q$ dependence of $\sigma_\text{eff}(q)$.