Amplitude

Quantum

Quantum gravity

Axion

Combinatorics

Physics

Scattering amplitude

Field theory (psychology)

Gravitation

Spacetime

Dark matter

Mathematics

Mathematical physics

Graviton

Theoretical physics

Quantum mechanics

f(R) gravity

Effective field theory

Particle physics

Massless particle

Conjecture

Classical mechanics

Physical Review Letters

The weak gravity conjecture---which posits that gravity must be the weakest force in theories of matter coupled to gravity---is shown to be satisfied as a general property of scattering matrices of effective field theories.

Positivity of Amplitudes, Weak Gravity Conjecture, and Modified Gravity