Off-shell Formulation of Higher-Spin Gravity Part I: Classical Action
We provide Vasiliev's fully nonlinear equations of motion for bosonic higher spin gauge fields in four spacetime dimensions with an action principle based on a generalized Hamiltonian sigma model. The action contains two types of interactions appearing in a Q-structure and in a generalized Poisson structure. We provide boundary conditions on fields and gauge parameters that are compatible with the variational principle and that make the system perturbatively equivalent, on-shell, to Vasiliev's original system.
Talk based on 1102.2219 [hep-th] by N. Boulanger and P. Sundell.