Four-dimensional solutions of supergravity on compact manifolds with flux are forbidden via a no-go theorem. In type IIB/F-theory, and heterotic/type I there are higher derivative metric couplings which allow one to evade this no-go theorem. However, M-theory and type IIA compactifications are distinguished: there are obvious candidate metric couplings, yet, one would expect such vacua to exist via duality arguments. I present evidence that such vacua do exist in virtue of new higher-derivative couplings. The couplings are distinct in that they involve metric and flux. I will also discuss some examples.

University of Surrey