Construction of an asymptotic S matrix for perturbative quantum gravity

Understand

The infrared behavior of perturbative quantum gravity is studied using the method developed for QED by Faddeev and Kulish.

• The operator describing the asymptotic dynamics is derived and used to construct an IR-finite S matrix and space of asymptotic states.
• All-orders cancellation of IR divergences is shown explicitly at the level of matrix elements for the example case of gravitational potential scattering.
• As a practical application of the formalism, the soft part of a scalar scattering amplitude is related to the gravitational Wilson line and computed to all orders.