Nonlinear Neutral Inclusions: Assemblages of Spheres
  If a neutral inclusion is inserted in a matrix containing a uniform applied electric field, it does not disturb the field outside the inclusion. The well known Hashin coated sphere is an example of a neutral coated inclusion. In this paper, we consider the problem of constructing neutral inclusions from nonlinear materials. In particular, we discuss assemblages of coated spheres and the two-dimensional analogous problem of assemblages of coated disks. 
Silvia Jim\'enez, Bogdan Vernescu and William Sanguinet
math-ph math.MP