High Energy Theory Seminar
Scattering in four-dimensional asymptotically flat spacetimes obeys an infinite-dimensional symmetry algebra that matches the structure of a two-dimensional conformal field theory living on the celestial sphere. This represents a new paradigm for identifying and organizing universal features of scattering amplitudes and for gaining insight into quantum gravity in the bulk asymptotically flat spacetime from the celestial boundary theory. I will exploit the map from plane wave asymptotic states to conformal primary wavefunctions to explore structures in amplitudes and classical solutions centered around the theme of shifting conformal dimensions and spin: (i) The striking relation between gauge theory and gravity amplitudes known as the double copy appears to be obscured in celestial amplitudes due to the lack of manifest translation symmetry, nevertheless, I will propose a well-defined celestial double copy which generalizes the usual squaring of numerators to operator-valued numerators acting on scalar amplitudes. (ii) A classical double copy structure is obeyed by conformal primary wavefunctions and their generalization to non-radiative wavefunctions among which we identify bulk solutions corresponding to shockwaves and boosted black holes. (iii) Finally, the notion of shifting spin and conformal dimension naturally leads us to descendancy relations amongst celestial CFT operators.
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