Duality Rotations in Nonlinear Electrodynamics and in Extended Supergravity

Understand

We review the general theory of duality rotations which, in four dimensions, exchange electric with magnetic fields.

• Necessary and sufficient conditions in order for a theory to have duality symmetry are established.
• A nontrivial example is Born-Infeld theory with n abelian gauge fields and with Sp(2n,R) self-duality.
• We then review duality symmetry in supergravity theories.