Compactness results and applications to some "zero mass" elliptic   problems
  In this paper we present some compactness results, showing how they can be applied in dealing with "zero mass" problems by a variational approach. In particular we use our results in two different situations: we look for complex valued solutions of a very classical elliptic equation, and we study an elliptic problem on an axially symmetric unbounded domain. 
Antonio Azzollini, Alessio Pomponio