Benjamin K. Tippett
In light of the surge in popularity of electromagnetic cloaking devices, we consider whether it is possible to use general relativity to cloak a volume of spacetime through gravitational lensing. A metric for such a spacetime geometry is presented, and its geometric and physical implications are explained.
In general relativity, there is a tradition of engineering spacetime geometries with exotic attributes previously seen only in science ﬁction. Tipler  and Morris  have introduced time machines; and Alcubierre  introduced a warp drive. In science ﬁction, one popular conceit is the idea of a cloaking device: a mechanism through which a spaceship could be made undetectable. The revelation that curved spaces can be matched to the electromagnetic properties of a medium has sparked a recent interest in optical cloaking [1, 3–6, 8, 10]. We seek to construct a spacetime geometry which cloaks an interior region from null geodesics….
Read more: http://arxiv.org/PS_cache/arxiv/pdf/1108/1108.3793v1.pdf