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arXiv 1206.5987math.APmath-phmath.MP
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麦克斯韦方程组的逆散射问题

Inverse scattering problem for the Maxwell's equations

A. G. Ramm

摘要:

讨论了麦克斯韦方程组的逆散射问题。本文将Maxwell系统约化为一个新的具有{ \it标量弱奇异核}的Fredholm第二类积分方程。这个方程允许人们推导出散射振幅的公式,其中只有一个标量函数。如果这个函数很小(验证Born型近似的假设),则从散射数据获得逆问题的解的公式:有界区域$D\subset \R^3$中的复介电常数$\ep'(x)$由对于固定$k=ω\sqrt{\ep_0 μ_0}>0$和所有$β,α\in S^2$已知的散射幅度$A(β,α,k)$得到,其中$S^2$是$\R^3$中的单位球,$\ep_0$和$μ_0$是外部区域$D'=\R^3 \setminus D$中的恒定介电常数和磁导率。本文中的{ \it新颖点}包括:i)将{ \it矢量EM波}的逆问题简化为{具有标量核的\it矢量积分方程},而无需对散射体的任何对称性假设,ii)推导用于求解逆散射问题的第一类{ \it标量积分方程},和iii)给出求解该标量积分方程的公式。该积分方程的求解是一个不适定问题。给出了该问题稳定解的方法。

英文摘要:

Inverse scattering problem is discussed for the Maxwell's equations. A reduction of the Maxwell's system to a new Fredholm second-kind integral equation with a {\it scalar weakly singular kernel} is given for electromagnetic (EM) wave scattering. This equation allows one to derive a formula for the scattering amplitude in which only a scalar function is present. If this function is small (an assumption that validates a Born-type approximation), then formulas for the solution to the inverse problem are obtained from the scattering data: the complex permittivity $\ep'(x)$ in a bounded region $D\subset \R^3$ is found from the scattering amplitude $A(β,α,k)$ known for a fixed $k=ω\sqrt{\ep_0 μ_0}>0$ and all $β,α\in S^2$, where $S^2$ is the unit sphere in $\R^3$, $\ep_0$ and $μ_0$ are constant permittivity and magnetic permeability in the exterior region $D'=\R^3 \setminus D$. The {\it novel points} in this paper include: i) A reduction of the inverse problem for {\it vector EM waves} to a {\it vector integral equation with scalar kernel} without any symmetry assumptions on the scatterer, ii) A derivation of the {\it scalar integral equation} of the first kind for solving the inverse scattering problem, and iii) Presenting formulas for solving this scalar integral equation. The problem of solving this integral equation is an ill-posed one. A method for a stable solution of this problem is given.

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