On Nonlinear Higher Spin Curvature
  We present the first nonlinear term of the higher spin curvature which is covariant with respect to deformed gauge transformations that are linear in the field. We consider in detail the case of spin 3 after presenting spin 2 as an example, and then construct the general spin s quadratic term of the deWit-Freedman curvature. 
Ruben Manvelyan, Karapet Mkrtchyan, Werner R\"uhl, Murad Tovmasyan
hep-th gr-qc math-ph math.MP