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arXiv 1507.01730math.AP
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变号系数Helmholtz方程的极限吸收原理与适定性适定性

Limiting absorption principle and well-posedness for the Helmholtz equation with sign changing coefficients

Hoai-Minh Nguyen

摘要:

本文研究了负折射率材料的变号系数Helmholtz方程的极限吸收原理及其适定性。利用\cite{Ng-Complementary}中引入的反射技巧,我们首先从这些方程导出柯西问题。通过对这些柯西问题的各种先验估计,得到了极限吸收原理和适定性。提出了获得先验估计的方法。第一个如下先验估计椭圆系统配备一般补充边界条件,由于Agmon,道格拉斯,和Nirenberg在他们的经典工作\cite{ADNII}。第二种方法是对第一种方法的补充,它是变分的,基于狄利克雷原理。最后一种方法是对第二种方法的补充,它也是变分的,并使用乘数技术。因此,我们得到了关于这些方程的适定性的新结果,其中矩阵值系数的正性条件被部分或不严格地施加在变号系数的界面上。因此,即使在符号变化界面上的系数的对比度是任意的情况下,也可以保持适定性。这使我们能够重新发现和扩展的积分方法,伪微分算子理论,和T-曲率的方法所获得的结果。由极限吸收原理得到的唯一解通常为$H^1_{\loc}(\mR^d)$中的{ \bf not},$L^2_{\loc}(\mR^d)$中的{ \bf not even}也可能。我们的结果的最优性也进行了讨论。

英文摘要:

In this paper, we investigate the limiting absorption principle associated to and the well-posedness of the Helmholtz equations with sign changing coefficients which are used to model negative index materials. Using the reflecting technique introduced in \cite{Ng-Complementary}, we first derive Cauchy problems from these equations. The limiting absorption principle and the well-posedness are then obtained via various a priori estimates for these Cauchy problems. There approaches are proposed to obtain the a priori estimates. The first one follows from a priori estimates of elliptic systems equipped general complementing boundary conditions due to Agmon, Douglis, and Nirenberg in their classic work \cite{ADNII}. The second approach, which is complement to the first one, is variational and based on the Dirichlet principle. The last approach, which is complement to the second one, is also variational and uses the multiplier technique. As a consequence, we obtain new results on the well-posedness of these equations for which the positivity conditions concerning the matrix-valued coefficients are imposed partially or not strictly on the interface of sign changing coefficients. As a result, the well-posedness can hold even in the case the contrast of the coefficients across the sign changing interfaces is arbitrary. This allows us to rediscover and extend largely known results obtained by the integral method, the pseudo differential operator theory, and the T-coercivity approach. The unique solution, obtained by the limiting absorption principle, is {\bf not} in $H^1_{\loc}(\mR^d)$ as usual and possibly {\bf not even} in $L^2_{\loc}(\mR^d)$. The optimality of our results is also discussed.

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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