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arXiv 1607.01338math.AP
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具有双非线性"快"扩散的Fisher-KPP问题

The Fisher-KPP problem with doubly nonlinear "fast" diffusion

Alessandro Audrito, Juan Luis Vazquez

摘要:

著名的Fisher-KPP反应扩散模型将线性扩散与典型的Fisher-KPP反应项相结合,并出现在许多相关的应用中。这是显着的数学模型,因为在线性扩散的情况下,它拥有一个家庭的行波,描述了一个广泛的类解决方案的渐近行为$0\leq u(x,t)\leq 1$中提出的问题在真正的线。在"慢"和"伪线性"双非线性扩散的情况下也证实了有限速度传播波的存在,参见arXiv:1601.05718。在这里,我们调查相应的理论与“快速”双非线性扩散,我们发现,一般的解决方案显示出非TW渐近行为,并在空间中的指数传播的大时代。最后,我们证明了精确的界限的水平集的一般解决方案,即使我们的工作与空间维$N \geq 1$。特别是,我们表明,水平集的位置是近似线性的大时代,当我们采取空间对数尺度,找到一个强大的偏离线性的情况下,出现了著名的Bramson对数校正。

英文摘要:

The famous Fisher-KPP reaction diffusion model combines linear diffusion with the typical Fisher-KPP reaction term, and appears in a number of relevant applications. It is remarkable as a mathematical model since, in the case of linear diffusion, it possesses a family of travelling waves that describe the asymptotic behaviour of a wide class solutions $0\leq u(x,t)\leq 1$ of the problem posed in the real line. The existence of propagation wave with finite speed has been confirmed in the cases of "slow" and "pseudo-linear" doubly nonlinear diffusion too, see arXiv:1601.05718. We investigate here the corresponding theory with "fast" doubly nonlinear diffusion and we find that general solutions show a non-TW asymptotic behaviour, and exponential propagation in space for large times. Finally, we prove precise bounds for the level sets of general solutions, even when we work in with spacial dimension $N \geq 1$. In particular, we show that location of the level sets is approximately linear for large times, when we take spatial logarithmic scale, finding a strong departure from the linear case, in which appears the famous Bramson logarithmic correction.

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