Removable singularities for degenerate elliptic Pucci operators
  In this paper we introduce some fully nonlinear second order operators defined as weighted partial sums of the eigenvalues of the Hessian matrix, arising in geometrical contexts, with the aim to extend maximum principles and removable singularities results to cases of highly degenerate ellipticity.nn 
Giulio Galise and Antonio Vitolo
math.AP