Degenerate Whittaker functionals for real reductive groups
  In this paper we establish a connection between the associated variety of a representation and the existence of certain degenerate Whittaker functionals, for both smooth and K-finite vectors, for all quasi-split real reductive groups, thereby generalizing results of Kostant, Matumoto and others. 
Dmitry Gourevitch, Siddhartha Sahi
math.RT