Regularized Transformation-Optics Cloaking in Acoustic and   Electromagnetic Scattering
  We consider transformation-optics based cloaking in acoustic and electromagnetic scattering. The blueprints for an ideal cloak use singular acoustic and electromagnetic materials, posing server difficulties to both theoretical analysis and practical fabrication. In order to avoid the singular structures, various regularized approximate cloaking schemes have been developed. We survey these developments in this paper. We also propose some challenging issues for further investigation. 
Hongyu Liu and Gunther Uhlmann
math.AP math-ph math.MP