Professor Andrew Strominger, Gwill E. York Professor of Physics, Harvard University, presents "The Holographic Principle in Flat Space" part of the Bethe Lecture series.
Gravitational soft theorems imply that scattering amplitudes in any 4D quantum theory of gravity have a symmetry which acts like the 2D conformal group on the celestial sphere at lightlike infinity. This motivates efforts to holographically recast 4D quantum gravity as a 2D conformal field theory on the celestial sphere which I will describe.