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arXiv math/0112014math.AP
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Euler-泊松方程中的临界解

Critical Thresholds in Euler-Poisson Equations

Shlomo Engelberg, Hailiang Liu, Eitan Tadmor

摘要:

本文初步研究了与欧拉-泊松方程有关的一个新现象--所谓的临界阈值现象,其中全局光滑性与有限时间崩溃问题的答案取决于初始组态是否越过一个内在的${O}(1)$临界阈值.本文研究了一类Euler-泊松方程,从有无各种强迫机制的一维问题到具有几何对称性的多维各向同性模型。这些模型被证明承认一个临界阈值,这是让人想起的条件崩溃的波在海滩上,只有波超过一定的初始临界阈值的经验有限时间的故障,但否则他们顺利传播。同时,解的渐近长时间行为保持不变,与跨越这些初始阈值无关。一个恰当的例子是简单的一维问题,其中非受迫无粘Burgers解总是形成激波间断,除了增加初始剖面$u_0' \geq 0$的非一般情况。与此相反,我们证明了相应的零背景下的一维Euler-泊松方程,只要其初始$(ρ_0,u_0)$构型满足$u_0'\geq -\sqrt{2kρ_0}$,允许有限的临界负速度梯度,就有整体光滑解.作为典型的非线性对流问题之一是导致一个Ricatti方程,这是平衡的强迫作为一个“非线性共振”,这反过来又是负责这个临界阈值现象。

英文摘要:

We present a preliminary study of a new phenomena associated with the Euler-Poisson equations -- the so called critical threshold phenomena, where the answer to questions of global smoothness vs. finite time breakdown depends on whether the initial configuration crosses an intrinsic, ${O}(1)$ critical threshold. We investigate a class of Euler-Poisson equations, ranging from one-dimensional problem with or without various forcing mechanisms to multi-dimensional isotropic models with geometrical symmetry. These models are shown to admit a critical threshold which is reminiscent of the conditional breakdown of waves on the beach; only waves above certain initial critical threshold experience finite-time breakdown, but otherwise they propagate smoothly. At the same time,the asymptotic long time behavior of the solutions remains the same, independent of crossing these initial thresholds. A case in point is the simple one-dimensional problem where the unforced inviscid Burgers' solution always forms a shock discontinuity except for the non-generic case of increasing initial profile, $u_0' \geq 0$. In contrast, we show that the corresponding one dimensional Euler-Poisson equation with zero background has global smooth solutions as long as its initial $(ρ_0,u_0)$- configuration satisfies $u_0'\geq -\sqrt{2kρ_0}$, allowing a finite, critical negative velocity gradient. As is typical for such nonlinear convection problems one is led to a Ricatti equation which is balanced here by a forcing acting as a 'nonlinear resonance', and which in turn is responsible for this critical threshold phenomena.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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