Lecture notes prepared for the 2021 SAGEX PhD School in Amplitudes hosted by the
University of Copenhagen August 10th through 13th. Topics covered include: the …

The soft limits of scattering amplitudes have been extensively studied due to their essential
role in the computation of physical observables in collider physics. The universal …

Celestial holography proposes a duality between the gravitational $\mathcal {S} $-matrix
and correlators in a conformal field theory living on the celestial sphere. In this white paper …

A bstract A set of infinitesimal Virasoro L⊗ Virasoro R diffeomorphisms are presented which
act non-trivially on the horizon of a generic Kerr black hole with spin J. The covariant phase …

We show that the geometry of a black hole horizon can be described as a Carrollian
geometry emerging from an ultra-relativistic limit where the near-horizon radial coordinate …

A bstract We construct the boundary phase space in D-dimensional Einstein gravity with a
generic given co-dimension one null surface\(\mathcal {N}\) as the boundary. The …

We explore conformal primary wave functions for all half integer spins up to the graviton.
Half steps are related by supersymmetry, integer steps by the classical double copy. The …

A bstract The dynamics of black hole horizons has recently been linked to that of Carrollian
fluids. This results in a dictionary between geometrical quantities and those of a fluid with …

These notes are a transcript of lectures given by the author in the XVIII Modave summer
school in mathematical physics. The introduction is devoted to a detailed review of the …

We establish that boundary degrees of freedom associated with a generic codimension one
null surface in D-dimensional pure Einstein gravity naturally admit a thermodynamical …