The dual graviton in duality covariant theories

Abstract

We review (and elaborate on) the `dual graviton problem' in the context of duality covariant formulations of M-theory (exceptional field theories). These theories require fields that are interpreted as components of the dual graviton in order to build complete multiplets under the exceptional groups E$_{d(d)}$, $d=2,\ldots, 9$. Circumventing no-go arguments, consistent theories for such fields have been constructed by incorporating additional covariant compensator fields. The latter fields are needed for gauge invariance but also for on-shell equivalence with $D=11$ and type IIB supergravity. Moreover, these fields play a non-trivial role in generalized Scherk-Schwarz compactifications, as for instance in consistent Kaluza-Klein truncation on AdS$_4\times {\rm S}^7$.