Chiral higher-spin symmetry of the celestial twistor sphere

Abstract: We study the chiral higher-spin symmetry of the celestial twistor sphere via the chiral higher-spin algebras $\mathfrak{ca}$ associated with certain holomorphic higher-spin theories in twistor space. The chiral higher-spin algebras $\mathfrak{ca}$ are non-unitary $W_{1+\infty}[\mathfrak{g}]$ algebras in the sense that their higher-spin generators can have negative conformal dimensions. We study $\mathfrak{ca}$ up to first order in quantum correction. In particular, we show that the $\mathfrak{ca}$ associated with anomaly-free holomorphic twistorial higher-spin theories are associative themselves, while the chiral algebras associated with anomalous holomorphic twistorial higher-spin theories only become associative upon enlarging $\mathfrak{ca}$ by introducing suitable axionic currents. Furthermore, we compute four-dimensional form factors -- interpreted as genuine scattering amplitudes in the integrable sector -- via correlation functions of some chiral CFTs that can source higher-spin currents of $\mathfrak{ca}$ on the celestial twistor sphere. Notably, we observe that higher-spin form factors do not always vanish, suggesting the existence of some mysterious bulk theories.