Perturbing towards gravity: crossing channels in the D1-D5 CFT

In previous work we explored correlators of bare twists in bosonic orbifold CFT's, which have a universal behavior at large N. We were able to show that this universality comes from an underlying algebraic structure: the crossing channels are accounted for by fractional Virasoro mode excitations of the bare twists. We extend our previous work to the supersymmetric case relevant for the D1-D5 brane intersection, where again certain correlation functions have a universal structure at large N. We show for a set of chiral-primary and anti-chiral-primary fields that the crossing channels are again explained algebraically, this time using a subsector of the superconformal algebra to excite the primary twists. Further, the operator used to deform the CFT towards a gravity limit lies in the tower of fractionally excited primary operators, and so this algebraic approach should be useful when bridging the gap between the gravity and field theory limits.