Linear and nonlinear eigenvalue problems for Dirac systems in unbounded   domains
  We first study the linear eigenvalue problem for a planar Dirac system in the open half-line and describe the nodal properties of its solution by means of the rotation number. We then give a global bifurcation result for a planar nonlinear Dirac system in the open half-line. As an application, we provide a global continuum of solutions of the nonlinear Dirac equation which have a special form. 
Anna Capietto, Walter Dambrosio, Duccio Papini
math.CA