We reformulate the scattering amplitudes of 4D at space gauge theory and gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT structure exhibits an OPE constructed from 4D collinear singularities, as well as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic symmetries of 4D at space. We derive these results by recasting 4D dynamics in terms of a convenient foliation of flat space into 3D Euclidean AdS and Lorentzian dS geometries. Tree-level scattering amplitudes take the form of Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to CFT correlators via the (A)dS/CFT dictionary. The Ward identities for the 2D conserved currents are dual to 4D soft theorems, while the bulk-boundary propagators of massless (A)dS modes are superpositions of the leading and subleading Weinberg soft factors of gauge theory and gravity. In general, the massless (A)dS modes are 3D Chern-Simons gauge fields describing the soft, single helicity sectors of 4D gauge theory and gravity. Consistent with the topological nature of Chern-Simons theory, Aharonov-Bohm effects record the \tracks" of hard particles in the soft radiation, leading to a simple characterization of gauge and gravitational memories. Soft particle exchanges between hard processes define the Kac-Moody level and Virasoro central charge, which are thereby related to the 4D gauge coupling and gravitational strength in units of an infrared cutoff. Lastly, we discuss a toy model for black hole horizons via a restriction to the Rindler region.
Cheung, Clifford, et al. "4D scattering amplitudes and asymptotic symmetries from 2D CFT." Journal of High Energy Physics (Online), vol. 2017, no. 1, Jan. 2017. https://doi.org/10.1007/JHEP01(2017)112
Cheung, Clifford, de la Fuente, Anton, & Sundrum, Raman (2017). 4D scattering amplitudes and asymptotic symmetries from 2D CFT. Journal of High Energy Physics (Online), 2017(1). https://doi.org/10.1007/JHEP01(2017)112
Cheung, Clifford, de la Fuente, Anton, and Sundrum, Raman, "4D scattering amplitudes and asymptotic symmetries from 2D CFT," Journal of High Energy Physics (Online) 2017, no. 1 (2017), https://doi.org/10.1007/JHEP01(2017)112
@article{osti_1360787,
author = {Cheung, Clifford and de la Fuente, Anton and Sundrum, Raman},
title = {4D scattering amplitudes and asymptotic symmetries from 2D CFT},
annote = {We reformulate the scattering amplitudes of 4D at space gauge theory and gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT structure exhibits an OPE constructed from 4D collinear singularities, as well as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic symmetries of 4D at space. We derive these results by recasting 4D dynamics in terms of a convenient foliation of flat space into 3D Euclidean AdS and Lorentzian dS geometries. Tree-level scattering amplitudes take the form of Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to CFT correlators via the (A)dS/CFT dictionary. The Ward identities for the 2D conserved currents are dual to 4D soft theorems, while the bulk-boundary propagators of massless (A)dS modes are superpositions of the leading and subleading Weinberg soft factors of gauge theory and gravity. In general, the massless (A)dS modes are 3D Chern-Simons gauge fields describing the soft, single helicity sectors of 4D gauge theory and gravity. Consistent with the topological nature of Chern-Simons theory, Aharonov-Bohm effects record the \tracks" of hard particles in the soft radiation, leading to a simple characterization of gauge and gravitational memories. Soft particle exchanges between hard processes define the Kac-Moody level and Virasoro central charge, which are thereby related to the 4D gauge coupling and gravitational strength in units of an infrared cutoff. Lastly, we discuss a toy model for black hole horizons via a restriction to the Rindler region.},
doi = {10.1007/JHEP01(2017)112},
url = {https://www.osti.gov/biblio/1360787},
journal = {Journal of High Energy Physics (Online)},
issn = {ISSN 1029-8479},
number = {1},
volume = {2017},
place = {United States},
publisher = {Springer Berlin},
year = {2017},
month = {01}}
Bondi, Hermann; Van der Burg, M. G. J.; Metzner, A. W. K.
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, Vol. 269, Issue 1336, p. 21-52https://doi.org/10.1098/rspa.1962.0161
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, Vol. 270, Issue 1340, p. 103-126https://doi.org/10.1098/rspa.1962.0206