On the associativity of one-loop corrections to the celestial OPE
Kevin Costello, Natalie M. Paquette
TL;DR
This work shows that one-loop collinear singularities in a self-dual gauge-theory realization of celestial holography do not form an associative chiral algebra due to a twistor-space anomaly. The obstruction is cured by introducing an axion via a Green-Schwarz mechanism, which yields an associative chiral algebra and a compact, chiral-algebraic derivation of the standard one-loop QCD splitting amplitudes. The axion-extended framework also provides a simple formula for one-loop form factors of self-dual Yang-Mills with the operator (B^2)/2, matching QCD amplitudes with an axion and offering insights for special matter content and gauge groups. Overall, the paper connects twistor-space anomalies, Green-Schwarz cancelation, and celestial OPE associativity to produce concrete one-loop results and streamlined amplitude expressions.
Abstract
There has been recent interest in the question of whether QCD collinear singularities can be viewed as the OPE of a two-dimensional CFT. We analyze a version of this question for the self-dual limit of pure gauge theory (incorporating states of both helicities). We show that the known one-loop collinear singulaties do not form an associative chiral algebra. The failure of associativity can be traced to a novel gauge anomaly on twistor space. We find that associativity can be restored for certain gauge groups if we introduce an unusual axion, which cancels the twistor space anomaly by a Green-Schwarz mechanism. Alternatively, associativity can be restored for some gauge groups with carefully chosen matter.
