Notes on Ramond-Ramond spinors and bispinors in double field theory

The Ramond-Ramond sector of double field theory (DFT) can be described either as an O(D,D) spinor or an O(D-1,1) x O(1,D-1) bispinor. Both formulations may be related to the standard polyform expansion in terms of even or odd rank field strengths corresponding to IIA or IIB duality frames. The spinor approach is natural in a (bosonic) metric formulation of DFT, while the bispinor is indispensable for supersymmetric DFT. In these notes, we show how these two approaches may be covariantly connected using a spinorial version of the DFT vielbein, which flattens an O(D,D) spinor into a bispinor. We also elaborate on details of the bispinor formulation in both even and odd D and elaborate on the distinction between the IIA/IIB/IIA*/IIB* duality frames.