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arXiv 2102.13447math.AP
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具有先验有界梯度的进化问题

On evolutionary problems with a-priori bounded gradients

Miroslav Bulíček, David Hruška, Josef Málek

摘要:

研究了一类非线性发展偏微分方程,它可以看作是热传导方程的推广,其中温度梯度先验有界,而热通量仅提供\mbox{$L^1$-coercivity} .应用空间和时间上的高阶可微性技巧,选择一个特殊的加权范数(等价于$\mathbb{R}^d$中的欧氏范数),结合可积函数的精细性质,利用重整化解的概念,证明了一个初始空间周期问题的具有$L^1$ -可积通量的长时间大数据弱解的存在唯一性.如果这个参数小于$2/(d+1)$,其中$d$表示空间维度,我们得到更高的可积性的流量。由于所开发的方法不限于标量方程,我们也提出了一个类似的结果,非线性抛物型系统中的非线性,是严格凸函数的梯度,给出了一个先验$L^\infty$ -界的梯度未知的解决方案。

英文摘要:

We study a nonlinear evolutionary partial differential equation that can be viewed as a generalization of the heat equation where the temperature gradient is a~priori bounded but the heat flux provides merely \mbox{$L^1$-coercivity}. Applying higher differentiability techniques in space and time, choosing a special weighted norm (equivalent to the Euclidean norm in $\mathbb{R}^d$), incorporating finer properties of integrable functions and using the concept of renormalized solution, we prove long-time and large-data existence and uniqueness of weak solution, with an $L^1$-integrable flux, to an initial spatially-periodic problem for all values of a positive model parameter. If this parameter is smaller than $2/(d+1)$, where $d$ denotes the spatial dimension, we obtain higher integrability of the flux. As the developed approach is not restricted to a scalar equation, we also present an analogous result for nonlinear parabolic systems in which the nonlinearity, being the gradient of a strictly convex function, gives an a-priori $L^\infty$-bound on the gradient of the unknown solution.

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