Sharp bounds for the first eigenvalue and the torsional rigidity related   to some anisotropic operators
  We prove a sharp upper bound for the first Dirichlet eigenvalue of a class of nonlinear elliptic operators which includes the p-Laplace and the pseudo-p-Laplace operators. Moreover, we prove a stability result by means of a suitable isoperimetric deficity. Finally, we give a sharp lower bound for the anisotropic p-torsional rigidity. 
Francesco Della Pietra, Nunzia Gavitone
math.AP