Experimental model of topological defects in Minkowski space-time based on disordered ferrofluid: Magnetic monopoles, cosmic strings and the space-time cloak

Abstract

In the presence of an external magnetic field, cobalt nanoparticle-based ferrofluid forms a self-assembled hyperbolic metamaterial. The wave equation, which describes propagation of extraordinary light inside the ferrofluid, exhibits 2 + 1 dimensional Lorentz symmetry. The role of time in the corresponding effective three-dimensional Minkowski space-time 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 theymay exhibit strong similarities with such Minkowski space-time defects asmagneticmonopoles, cosmic strings and the recently proposed space-time cloaks. Experimental observations of such defects are described.