On duality symmetries of supergravity invariants

The role of duality symmetries in the construction of counterterms for maximal supergravity theories is discussed in a field-theoretic context from different points of view. These are: dimensional reduction, the question of whether appropriate superspace measures exist and information about non-linear invariants that can be gleaned from linearised ones. The former allows us to prove that F-term counterterms cannot be E₇₍₇₎-invariant in D = 4, N = 8 supergravity or E₆₍₆₎-invariant in D = 5 maximal supergravity. This is confirmed by the two other methods which can also be applied to D = 4 theories with fewer supersymmetries and allow us to prove that N = 6 supergravity is finite at three and four loops and that N = 5 supergravity is three-loop finite.