Exceptional Form of D=11 Supergravity

Eleven-dimensional supergravity reveals large exceptional symmetries upon reduction, in accordance with the U-duality groups of M theory, but their higher-dimensional geometric origin has remained a mystery. In this Letter, we show that D 11 supergravity can be extended to be fully covariant under the exceptional groups E-n(n), n = 6, 7, 8. Motivated by a similar formulation of double field theory we introduce an extended exceptional spacetime.'' We illustrate the construction by giving the explicit E-6(6) covariant form: the full D = 11 supergravity, in a 5 + 6 splitting of coordinates but without truncation, embeds into an E-6(6) covariant 5 + 27 dimensional theory. We argue that this covariant form likewise comprises type IIB supergravity.