Bidimensional sigma-models on symmetric spaces are known to possess an infinite number of global symmetries, related to their integrable structure. I will show that restoring an infinite-dimensional gauge freedom in the formulation of such a theory makes “hidden” symmetries manifest. The finite model is seen as the solution of a gauge-invariant selfduality constraint in a sigma-model with an infinite-dimensional symmetric space as target-space. Beyond sigma-models on flat d=2 spacetime, this applies to d=2 reduction of M-theory or gravity, where the target-space is built on the semi-direct product of an affine group by the Witt group.

Service de Physique Théorique et MathématiqueUniversité Libre de Bruxelles