Skyrme Crystal from a Twisted Instanton on a Four-Torus
  We describe how an approximation to the minimal energy Skyrme crystal can be obtained from the holonomy of a Yang-Mills instanton. The appropriate instanton is twisted on a four-torus and has instanton number equal to one half. It generates a Skyrme field with the correct topological and symmetry properties of the crystal. An explicit solution for the instanton is not known, but an analytical fit to numerical data is available and using this we obtain a Skyrme crystal whose energy is only 2 percent above that of the (numerically) known solution. 
Nick Manton and Paul Sutcliffe