Null curve evolution in four-dimensional pseudo-Euclidean spaces
  We define a Lie bracket on a certain set of local vector fields along a null curve in a 4-dimensional semi-Riemannian space form. This Lie bracket will be employed to study integrability properties of evolution equations for null curves in a pseudo-Euclidean space. In particular, a geometric recursion operator generating infinite many local symmetries for the null localized induction equation is provided. 
Jos\'e del Amor, \'Angel Gim\'enez and Pascual Lucas
math-ph math.MP