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arXiv 2401.01437math.AP
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具有物理边界条件的趋化模型边界层收敛性 I:退化初始数据

Convergence of boundary layers of chemotaxis models with physical boundary conditions I: degenerate initial data

Jose Antonio Carrillo, Guangyi Hong, Zhi-an Wang

AI总结:

本文研究一维物理边界条件趋化-流体模型,通过取原函数、Hardy 不等式与加权能量估计,证明小氧气扩散率下边界层解收敛为外层解加内层解。

摘要:

Tuval 等人的著名实验表明,生活在水滴中的细菌可在气-水界面附近形成薄层,为此他们提出了一个具有物理边界条件的所谓趋化-流体系统,并结合数值模拟来解释这种模式形成背后的机制。然而,对所提出模型的边界层解的存在性与收敛性给出严格证明仍是一个开放问题。本文证明,在一维情形下,文献中提出的具有物理边界条件的模型在氧气扩散率 $\varepsilon>0$ 很小时能够产生边界层解。具体而言,我们证明当 $\varepsilon\rightarrow 0$ 时,具有 $\varepsilon>0$ 的模型解将收敛到 $\varepsilon=0$ 时的解(外层解)加上边界层廓线(内层解),后者在边界附近具有急剧转变。我们的分析存在两大困难。第一,模型的整体适定性难以证明,因为 Dirichlet 边界条件无法为模型中的交叉扩散结构提供所需的梯度估计。借助取原函数的技巧,我们消除了交叉扩散结构,使 Dirichlet 边界条件能够促进所需估计。第二,细菌密度的外层廓线要求在 $t\rightarrow 0^+$ 时于边界处退化,这使传统抵消技巧失效。这里我们采用 Hardy 不等式和精细的加权能量估计来克服这一障碍,并导出必要的关于 $\varepsilon$ 一致的估计,从而能够取极限 $\varepsilon\to 0$ 并得到结果。

英文摘要:

The celebrated experiment of Tuval et al. \cite{tuval2005bacterial} showed that the bacteria living a water drop can form a thin layer near the air-water interface, where a so-called chemotaxis-fluid system with physical boundary conditions was proposed to interpret the mechanism underlying the pattern formation alongside numerical simulations. However, the rigorous proof for the existence and convergence of the boundary layer solutions to the proposed model still remains open. This paper shows that the model with physical boundary conditions proposed in \cite{tuval2005bacterial} in one dimension can generate boundary layer solution as the oxygen diffusion rate $\varepsilon>0$ is small. Specifically, we show that the solution of the model with $\varepsilon>0$ will converge to the solution with $\varepsilon=0$ (outer-layer solution) plus the boundary layer profiles (inner-layer solution) with a sharp transition near the boundary as $ \varepsilon \rightarrow 0$. There are two major difficulties in our analysis. First, the global well-posedness of the model is hard to prove since the Dirichlet boundary condition can not contribute to the gradient estimates needed for the cross-diffusion structure in the model. Resorting to the technique of taking anti-derivative, we remove the cross-diffusion structure such that the Dirichlet boundary condition can facilitate the needed estimates. Second, the outer-layer profile of bacterial density is required to be degenerate at the boundary as $ t \rightarrow 0 ^{+}$, which makes the traditional cancellation technique incapable. Here we employ the Hardy inequality and delicate weighted energy estimates to overcome this obstacle and derive the requisite uniform-in-$\varepsilon$ estimates allowing us to pass the limit $\varepsilon \to 0$ to achieve our results.

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