On the Role of Massive Particles in Celestial Holography

Celestial holography is built upon the premise that scattering in quantum gravity can be entirely captured by a dual conformal field theory living on the celestial sphere at null infinity. While massive particles do not reach null infinity, kinematic symmetries alone are known to be powerful enough to supply a prescription for incorporating massive particles into the celestial holographic framework. Remarkably, massless scattering particles are also known to transform under an even larger symmetry group: w_(1+infinity), which might in turn provide even stronger constraints on dynamics in celestial holography. I will explain how massive particles appear at present to be far more exotic objects in celestial holography but nevertheless likewise transform non-trivially under w_(1+infinity).