N=2 and N=4 supergravities as compactifications from string theories in 10 dimensions

We first review standard results of the compactification of type IIA and IIB supergravities on a Calabi-Yau threefold and illustrate mirror symmetry. Then we compactify the same theories on a class of generalized Calabi-Yau manifolds called Half-flat. We obtain the scalar potential, and we show that type IIA on a Half-flat manifold is mirror symmetric to type IIB on a Calabi-Yau threefold with electric NS-fluxes turned on. In the last part, we compute the full equations of motion for N=4 supergravity in central charge superspace with the graviphotons identified as central charge components of the vielbein. We show the equivalence with the formulation in components.