Light-ray Operators and the BMS Algebra

Abstract

We study light-ray operators constructed from the energy-momentum tensor in $d$-dimensional Lorentzian conformal field theory. These include in particular the average null energy operator. The commutators of parallel light-ray operators on a codimension one light-sheet form an infinite-dimensional algebra. We determine this light-ray algebra and find that the $d$-dimensional (generalized) BMS algebra, including both the supertranslation and the superrotation, is a subalgebra. We verify this algebra in correlation functions of free scalar field theory. We also determine the infinite-dimensional algebra of light-ray operators built from non-abelian spin-one conserved currents.