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抛物型方程中加权梯度的强收敛及其在交叉扩散系统全局广义可解性中的应用

Strong convergence of weighted gradients in parabolic equations and applications to global generalized solvability of cross-diffusive systems

Mario Fuest

AI总结:

本文证明了抛物型方程初边值问题解的加权梯度强收敛性,并以此为基础,在无需对称性假设和参数小性条件下,建立了具有超线性增长源项的交叉扩散系统在任意空间维度下的全局广义可解性。

摘要:

在本文的第一部分,我们证明了 $(v_{0 \varepsilon})_{\varepsilon \in (0, 1)}$ 在 $L^1(Ω)$ 中的强收敛和 $(f_{\varepsilon})_{\varepsilon \in (0, 1)}$ 在 $L_{\textrm{loc}}^1(\overline Ω\times [0, \infty))$ 中的弱收敛,不仅足以得出我们在光滑有界区域 $Ω$ 中考虑的初边值问题 \begin{align*} \begin{cases} v_{\varepsilon t} = Δv_\varepsilon + f_\varepsilon(x, t) & \text{在 $Ω\times (0, \infty)$ 中}, \\\\ \partial_νv_\varepsilon = 0 & \text{在 $\partial Ω\times (0, \infty)$ 上}, \\\\ v_\varepsilon(\cdot, 0) = v_{0 \varepsilon} & \text{在 $Ω$ 中}, \end{cases} \end{align*} 的解收敛于极限问题的唯一弱解,而且 $v_\varepsilon$ 的某些加权梯度也会沿某子序列在 $L_{\textrm{loc}}^2(\overline Ω\times [0, \infty))$ 中强收敛。然后我们利用这些结果获得了各种交叉扩散系统的全局广义解。此外,我们还建立了系统 \begin{align*} \begin{cases} u_t = Δu - χ\nabla \cdot (\frac{u}{v} \nabla v) + g(u), \\\\ v_t = Δv - uv, \end{cases} \end{align*} 的全局广义可解性,其中 $χ> 0$ 和 $g \in C^1([0, \infty))$ 是给定的,仅需($g(0) \geq 0$ 且)$-g$ 超线性增长。该结果在所有空间维度中均成立,既不需要任何对称性假设,也不需要某些参数的小性条件。从而,我们扩展了 Lankeit 和 Lankeit (Nonlinearity, 32(5):1569--1596, 2019) 关于二次增长的 $-g$ 所证明的相应结果。

英文摘要:

In the first part of the present paper, we show that strong convergence of $(v_{0 \varepsilon})_{\varepsilon \in (0, 1)}$ in $L^1(Ω)$ and weak convergence of $(f_{\varepsilon})_{\varepsilon \in (0, 1)}$ in $L_{\textrm{loc}}^1(\overline Ω\times [0, \infty))$ not only suffice to conclude that solutions to the initial boundary value problem \begin{align*} \begin{cases} v_{\varepsilon t} = Δv_\varepsilon + f_\varepsilon(x, t) & \text{in $Ω\times (0, \infty)$}, \\ \partial_νv_\varepsilon = 0 & \text{on $\partial Ω\times (0, \infty)$}, \\ v_\varepsilon(\cdot, 0) = v_{0 \varepsilon} & \text{in $Ω$}, \end{cases} \end{align*} which we consider in smooth, bounded domains $Ω$, converge to the unique weak solution of the limit problem, but that also certain weighted gradients of $v_\varepsilon$ converge strongly in $L_{\textrm{loc}}^2(\overline Ω\times [0, \infty))$ along a subsequence. We then make use of these findings to obtain global generalized solutions to various cross-diffusive systems. Inter alia, we establish global generalized solvability of the system \begin{align*} \begin{cases} u_t = Δu - χ\nabla \cdot (\frac{u}{v} \nabla v) + g(u), \\ v_t = Δv - uv, \end{cases} \end{align*} where $χ> 0$ and $g \in C^1([0, \infty))$ are given, merely provided that ($g(0) \geq 0$ and) $-g$ grows superlinearily. This result holds in all space dimensions and does neither require any symmetry assumptions nor the smallness of certain parameters. Thereby, we expand on a corresponding result for quadratically growing $-g$ proved by Lankeit and Lankeit (Nonlinearity, 32(5):1569--1596, 2019).

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