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arXiv 1903.03354math.AP
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具有弱正则非线性项的Whitham型色散发展方程中的孤波

Solitary waves in dispersive evolution equations of Whitham type with nonlinearities of mild regularity

Fredrik Hildrum

摘要:

在Sobolev空间${\mathrm{H}^s}$,${ s > 0 }$中证明了一类非线性色散发展方程\begin{equation*} u_t + \left(Lu+ n(u)\right)_x = 0, \end{equation*}的小孤波解和周期行波解的存在性,其中色散${L}$是一个负阶Fourier乘子,其符号在低频为KdV型,具有可积的Fourier逆${ K }$,非线性${n}$是非齐次的,局部Lipschitz和超线性增长的起源。这概括了Ehrnström,Groves & Wahlén在一类方程上的早期工作,其中包括Whitham的表面重力水波模型方程,具有精确的线性色散关系。工具涉及约束变分方法,狮子的浓度紧凑性原则,一个强有力的分数链规则的组成运营商的低相对规律性,并切断参数${n}$,使我们能够低于典型的${s > \frac{1}{2}}$制度。我们还证明了当${ K }$是非负的时,这些解要么是上升波,要么是下降波,并且当${ n }$太强时,这些解不存在。

英文摘要:

We show existence of small solitary and periodic traveling-wave solutions in Sobolev spaces ${\mathrm{H}^s}$, ${ s > 0 }$, to a class of nonlinear, dispersive evolution equations of the form \begin{equation*} u_t + \left(Lu+ n(u)\right)_x = 0, \end{equation*} where the dispersion ${L}$ is a negative-order Fourier multiplier whose symbol is of KdV type at low frequencies and has integrable Fourier inverse ${ K }$ and the nonlinearity ${n}$ is inhomogeneous, locally Lipschitz and of superlinear growth at the origin. This generalises earlier work by Ehrnström, Groves & Wahlén on a class of equations which includes Whitham's model equation for surface gravity water waves featuring the exact linear dispersion relation. Tools involve constrained variational methods, Lions' concentration-compactness principle, a strong fractional chain rule for composition operators of low relative regularity, and a cut-off argument for ${n}$ which enables us to go below the typical ${s > \frac{1}{2}}$ regime. We also demonstrate that these solutions are either waves of elevation or waves of depression when ${ K }$ is nonnegative, and provide a nonexistence result when ${ n }$ is too strong.

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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