Duality and Axionic Weak Gravity

Understand

The axionic weak gravity conjecture predicts the existence of instantons whose actions are less than their charges in appropriate units.

• We show that the conjecture is satisfied for the axion-dilaton-gravity system if we assume duality constraints on the higher derivative corrections in addition to positivity bounds which follow from unitarity, analyticity, and locality of UV scattering amplitudes.
• On the other hand, the conjecture does not follow if we assume the positivity bounds only.
• This presents an example where derivation of the weak gravity conjecture requires more detailed UV information than the consistency of scattering amplitudes.