Metamaterial cloaking

Summary

Metamaterial cloaking is the use of an engineered medium to make an object invisible to electromagnetic waves. A shell of metamaterial around a region guides the waves around it. An observer outside then sees the same field as if the region and the shell were empty space. The main design tool is transformation optics, which maps a punctured ball onto a shell. It is an example of non-uniqueness in electromagnetic scattering and in inverse problems: different media can give the same measurements outside.