## New Approach to Nonlinear Electrodynamics: Dualities as Symmetries of Interaction

The duality-symmetric nonlinear electrodynamics in a new formulation with auxiliary tensor fields is considered. The Maxwell field strength appears only in bilinear terms of the corresponding generic Lagrangian, while the self-interaction is represented by a function E depending on the auxiliary fields. Two types of dualities inherent in the nonlinear electrodynamics admit a simple off-shell characterization as symmetry properties of this function. In the standard formulation, the continuous U(1) duality symmetry is nonlinearly realized on the Maxwell field strength. In the new setting, the same symmetry acts as linear U(1) transformations of the auxiliary field variables. The nonlinear U(1) dualitymore »