Three-graviton amplitude in Berkovits–Vafa–Witten variables

We compute the three-graviton tree amplitude in Type IIB superstring theory compactified to six dimensions using the manifestly (6d) supersymmetric Berkovits–Vafa–Witten worldsheet variables. We consider two cases of background geometry: the flat space example R6×K3, and the curved example AdS3×S3×K3 with Ramond flux, and compute the correlation functions in the bulk.