Non-semisimple and Complex Gaugings of N = 16 Supergravity

Maximal and non-maximal supergravities in three dimensions allow for a large variety of semisimple (Chern-Simons) gauge groups. In this paper, we analyze non-semisimple and complex gauge groups that satisfy the pertinent consistency relations for a maximal (N = 16) gauged supergravity to exist. We give a general procedure how to generate non-semisimple gauge groups from known admissible semisimple gauge groups by a singular boost within E 8(8). Examples include the theories with gauge group SO(8) × T 28 that describe the reduction of IIA/IIB supergravity on the seven-sphere. In addition, we exhibit two 'strange embeddings' of the complex gauge group SO(8, C) into (real) E 8(8) and prove that both can be consistently gauged. We discuss the structure of the associated scalar potentials as well as their relation to those of D ≥ 4 gauged supergravities.