Type IIB Theory on Half-flat Manifolds

In this note we derive the low-energy effective action of type IIB theory compactified on half-flat manifolds and we show that this precisely coincides with the low-energy effective action of type IIA theory compactified on a Calabi–Yau manifold in the presence of NS three-form fluxes. We provide in this way a further check of the recently formulated conjecture that half-flat manifolds appear as mirror partners of Calabi–Yau manifolds when NS fluxes are turned on. December 2002 Work supported by: the CNRS – the French Center for National Scientific Research, DFG – The German Science Foundation and DAAD – the German Academic Exchange Service. On leave from IFIN-HH Bucharest