对“真空对重力辅助光的负光的折射”的评论
Comment on 'Towards gravitationally assisted negative refraction of light by vacuum'
摘要：
参考文献arXiv：physics/0408021声称时空的无物质区域可以支持电磁波，对于电磁波，相速度3矢量与功率流3矢量方向相反。这是\cite{ML}中采用的负屈光定义。我们在这里表明，这不可能发生在电磁能量密度为正的时空区域。
英文摘要：
Reference arXiv:physics/0408021 claims that matter--free regions of spacetime may support electromagnetic waves for which the phase velocity 3-vector is oppositely directed to the power flow 3-vector. This was the definition of negative refraction adopted in \cite{ML}. We here show that this cannot occur in regions of spacetime for which the electromagnetic energy density is positive.
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