Hidden topological structure in the continuous Heisenberg spin chain
  In order to study the spin configurations of the classical one-dimensional Heisenberg model, we map the normalized unit vector, representing the spin, to a space curve. We show that the total chirality of the configuration is a conserved quantity. When the space curve forms a knot, this defines a new class of topological spin configurations for the Heisenberg model. 
R. Dandoloff