- Northeastern University
Celestial sphere is the sphere of all directions in the sky. When two relativistic observers compare snapshots of the night sky, they find them related by conformal transformations. According to a novel proposal of flat spacetime holography, four-dimensional physics is encoded in the properties of two-dimensional conformal field theory describing celestial sphere at null infinity. In this framework, the scattering amplitudes of elementary particles are represented by conformal correlation functions. Well-known soft theorems appear as Ward identities reflecting asymptotic symmetries. This may offer new insights into some mysterious connections between gauge theories and gravity.