Classical Lagrangians for Momentum Dependent Lorentz Violation
  Certain momentum-dependent terms in the fermion sector of the Lorentz-violating Standard Model Extension (SME) yield solvable classical lagrangians of a type not mentioned in the literature. These cases yield new relatively simple examples of Finsler and pseudo-Finsler structures. One of the cases involves antisymmetric $d$-type terms and yields a new example of a relatively simple covariant lagrangian. 
Don Colladay and Patrick McDonald
hep-ph math.DG