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arXiv 2009.07598math.AP
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截止卢瑟福散射截面接近麦克斯韦的玻尔兹曼方程

Boltzmann equation with cutoff Rutherford scattering cross section near Maxwellian

Ling-Bing He, Yu-Long Zhou

摘要:

著名的卢瑟福微分截面,表示为$ dΩ/dσ$,对应于库仑势的两体相互作用。它导致动量传递(或输运截面)的数学发散,其由$$\int_{{\mathbb S}^2} (1-\cosθ) \frac{dΩ}{dσ} dσ\sim \int_0^π θ^{-1}dθ. $$描述,其中$θ$是散射事件中的偏离角。由于屏蔽效应,物理上可以假设$θ_{\min}$是散射仍然可以被认为是库仑散射的最小角度的数量级。在偏差角L的临时截止点$θ\geq θ_{\min}$下。D.朗道在\cite{landau1936transport}中导出了一个新的弱相互作用气体方程,现在称为福克-普朗克-朗道方程。在目前的工作中,我们建立了一个统一的框架来证明朗道的正式推导\cite{landau1936transport}和所谓的朗道近似问题提出的\cite{alexandre2004landau}在接近平衡制度。准确地说,(i)。我们证明了具有截断卢瑟福截面的Boltzmann方程的整体适定性,该截断卢瑟福截面可能是相对速度和偏差角最奇异的核。(ii)。我们证明了Boltzmann方程和Landau方程的解之间具有对数精度的时间上的全局误差估计,这与著名的库仑对数是一致的。这些结果的证明的关键成分包括一个完整的线性化玻尔兹曼碰撞算子,一个统一的谱隙估计和一个新的线性-准线性方法的bavity估计。

英文摘要:

The well-known Rutherford differential cross section, denoted by $ dΩ/dσ$, corresponds to a two body interaction with Coulomb potential. It leads to the logarithmically divergence of the momentum transfer (or the transport cross section) which is described by $$\int_{{\mathbb S}^2} (1-\cosθ) \frac{dΩ}{dσ} dσ\sim \int_0^π θ^{-1}dθ. $$ Here $θ$ is the deviation angle in the scattering event. Due to screening effect, physically one can assume that $θ_{\min}$ is the order of magnitude of the smallest angles for which the scattering can still be regarded as Coulomb scattering. Under ad hoc cutoff $θ\geq θ_{\min}$ on the deviation angle, L. D. Landau derived a new equation in \cite{landau1936transport} for the weakly interacting gas which is now referred to as the Fokker-Planck-Landau or Landau equation. In the present work, we establish a unified framework to justify Landau's formal derivation in \cite{landau1936transport} and the so-called Landau approximation problem proposed in \cite{alexandre2004landau} in the close-to-equilibrium regime. Precisely, (i). we prove global well-posedness of the Boltzmann equation with cutoff Rutherford cross section which is perhaps the most singular kernel both in relative velocity and deviation angle. (ii). we prove a global-in-time error estimate between solutions to Boltzmann and Landau equations with logarithm accuracy, which is consistent with the famous Coulomb logarithm. Key ingredients into the proofs of these results include a complete coercivity estimate of the linearized Boltzmann collision operator, a uniform spectral gap estimate and a novel linear-quasilinear method.

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