Bispinor Auxiliary Fields in Duality-Invariant Electrodynamics Revisited
  Motivated by a recent progress in studying the duality-symmetric models of nonlinear electrodynamics, we revert to the auxiliary tensorial (bispinor) field formulation of the O(2) duality proposed by us in arXiv:hep-th/0110074, arXiv:hep-th/0303192. In this approach, the entire information about the given duality-symmetric system is encoded in the O(2) invariant interaction Lagrangian which is a function of the auxiliary fields V_{\alpha\beta}, \bar V_{\dot \alpha\dot \beta}. We extend this setting to duality-symmetric systems with higher derivatives and show that the recently employed "nonlinear twisted self-duality constraints" amount to the equations of motion for the auxiliary tensorial fields in our approach. Some other related issues are briefly discussed and a few instructive examples are explicitly worked out. 
E. A. Ivanov, B. M. Zupnik
hep-th