Dimensional reduction of type IIB supergravity and exceptional quaternionic manifolds

The authors describe the SU(3) invariant reduction of the type IIB supergravity from ten to four dimensions, and show that the low-energy scalars parametrise the quaternionic sigma model G 2,2 /SO(4). They identify the scalar Lagrangian with the one obtained from a similar SU(3) truncation of the type IIA theory, followed by a dimensional reduction to three dimensions. This is an explicit realisation of the c map, that in general relates the low-energy Lagrangians of the type-II superstrings when compactified on the same (2, 2) superconformal theory.