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arXiv 2203.01038math-phcond-mat.stat-mechmath.APmath.MP
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用匹配渐近法研究两种群排斥过程的宏观行为

Macroscopic behaviour in a two-species exclusion process via the method of matched asymptotics

James Mason, Robert L Jack, Maria Bruna

摘要:

考虑周期格点上的两种群简单排斥过程。我们使用的方法匹配渐近推导出的两个人口密度在稀制度的发展方程,即交叉扩散系统的偏微分方程的两个物种密度。首先,我们的结果捕捉到了在平均场方法中被忽略的非平凡相互作用项,包括具有显式密度依赖性的非对角迁移率矩阵。其次,它概括了严格的流体动力学限制Quastel [Commun. Pure Appl.Math.45(6),623- 679(1992)],对于具有相等跳跃率的物种有效,并根据非显式自扩散系数给出,对于稀释区中不等速率的情况。在等速率的情况下,通过结合匹配的渐近近似在低密度和高密度的限制,我们得到一个三次多项式近似的自扩散系数,是数值上准确的所有密度。这种立方近似与数值模拟非常吻合。它也符合泰勒展开的二阶密度的自扩散系数使用严格的递归方法获得。

英文摘要:

We consider a two-species simple exclusion process on a periodic lattice. We use the method of matched asymptotics to derive evolution equations for the two population densities in the dilute regime, namely a cross-diffusion system of partial differential equations for the two species densities. First, our result captures non-trivial interaction terms neglected in the mean-field approach, including a non-diagonal mobility matrix with explicit density dependence. Second, it generalises the rigorous hydrodynamic limit of Quastel [Commun. Pure Appl. Math. 45(6), 623--679 (1992)], valid for species with equal jump rates and given in terms of a non-explicit self-diffusion coefficient, to the case of unequal rates in the dilute regime. In the equal-rates case, by combining matched asymptotic approximations in the low- and high-density limits, we obtain a cubic polynomial approximation of the self-diffusion coefficient that is numerically accurate for all densities. This cubic approximation agrees extremely well with numerical simulations. It also coincides with the Taylor expansion up to the second-order in the density of the self-diffusion coefficient obtained using a rigorous recursive method.

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