Generalised G2-structures and type IIB superstrings -: art. no. 053

The recent mathematical literature introduces generalised geometries which are defined by a reduction from the structure group SO(d, d) of the vector bundle T-2(2)d Td* to a special subgroup. In this article we show that compactification of IIB superstring vacua on 7-manifolds with two covariantly constant spinors leads to a generalised G(-structure associated with a reduction from SO(7; 7) to G) (x G)(. We also consider compactifications on 6-manifolds where analogously we obtain a generalised SU(3)-structure associated with SU(3) x SU(3), and show how these relate to generalised G)(2)(2)-structures.