Session L01: Soft Graviton and Gauge Amplitudes, Asymptotic Symmetries, and Bootstrap

Collider Tools for Classical Gravity

I will summarize recent progress in the program to apply tools developed for computing cross sections in collider physics to problems in classical general relativity. This effort has produced state-of-the-art computations of a wide range of observables and quantities relevant for current and future gravitational wave detectors, which I will describe.   

Shadows and Soft Exchange in Celestial CFT

I will discuss exponentiated soft exchange in (d+2)-dimensional gauge and gravitational theories using the celestial CFT formalism. These models exhibit spontaneously broken asymptotic symmetries generated by gauge transformations with non-compact support, and the effective dynamics of the associated Goldstone "edge" mode is expected to be d-dimensional. The introduction of an infrared regulator also explicitly breaks these symmetries so the edge mode in the regulated theory is really a d-dimensional pseudo-Goldstone boson. Symmetry considerations determine the leading terms in the effective action, whose coefficients are controlled by the infrared cutoff. Computations in this model reproduce the abelian infrared divergences in d=2, and capture the re-summed (infrared finite) soft exchange in higher dimensions. The model also reproduces the leading soft theorems in gauge and gravitational theories in all dimensions. Interestingly, we find that it is the shadow transform of the Goldstone mode that has local d-dimensional dynamics: the effective action expressed in terms of the Goldstone mode is non-local for d>2. The analysis demonstrates that symmetry principles suffice to calculate soft exchange in gauge theory and gravity.   

New Symmetries in Celestial Holography

Celestial holography represents a new approach to quantum gravity in asymptotically flat spacetimes in which the gravitational scattering problem is recast in terms of conformally covariant correlations on the celestial sphere. This talk will focus on the properties of gravitational scattering that support the existence of a two-dimensional holographic theory that governs these correlations.  A particular emphasis will be placed on a promising infinite-dimensional symmetry algebra known as w(1+infinity).