  Cobalt nanoparticle-based ferrofluid in the presence of external magnetic
field forms a self-assembled hyperbolic metamaterial. Wave equation describing
propagation of extraordinary light inside the ferrofluid exhibits 2+1
dimensional Lorentz symmetry. The role of time in the corresponding effective
3D Minkowski spacetime is played by the spatial coordinate directed along the
periodic nanoparticle chains aligned by the magnetic field. Here we present a
microscopic study of point, linear, planar and volume defects of the
nanoparticle chain structure and demonstrate that they may exhibit strong
similarities with such Minkowski spacetime defects as magnetic monopoles,
cosmic strings and the recently proposed spacetime cloaks. Experimental
observations of such defects are described.
