Existence of ground state solutions to Dirac equations with vanishing   potentials at infinity
  In this work we study the existence of ground-state solutions of Dirac equations with potentials which are allowed to vanish at infinity. The approach is based on minimization of the energy functional over a generalized Nehari set. Some conditions on the potentials are given in order to overcome the lack of compactness. 
Giovany M. Figueiredo, Marcos T. O. Pimenta
math.AP