Fractal bodies invisible in 2 and 3 directions
  We study the problem of invisibility for bodies with a mirror surface in the framework of geometrical optics. We show that for any two given directions it is possible to construct a two-dimensional fractal body invisible in these directions. Moreover, there exists a three-dimensional fractal body invisible in three orthogonal directions. The work continues the previous study in [A. Aleksenko and A. Plakhov. Bodies of zero resistance and bodies invisible in one direction. Nonlinearity 22, 1247-1258 (2009)], [A Plakhov and V Roshchina. Invisibility in billiards. Nonlinearity 24, 847-854 (2011)], where two-dimensional bodies invisible in one direction and three-dimensional bodies invisible in one and two orthogonal directions were constructed. 
Alexander Plakhov and Vera Roshchina
math.DS