Weak gravity versus scale separation

Understand

We give evidence that fully supersymmetric Anti-de Sitter vacua of extended supergravity with a residual gauge group containing an abelian factor cannot be scale separated as a consequence of the weak gravity conjecture.

• We prove this for N=2 and N=8 supergravity and we explain how our argument applies also to vacua with partially broken, but extended residual supersymmetry.
• We finally discuss possible loopholes and especially how certain N=1 models can evade our reasoning.
• Our results suggest that N=0,1 supersymmetry at the lagrangian level might be the most promising chances to obtain a truly four-dimensional effective description of quantum gravity.