cubic region. In type IIB this is simply the large volume regime. In type IIA, we have to be in the large volume and also in the “large complex structure limit”.

We now break $\caln=2$ to $\caln=1$ by an orientifold action and fluxes. After the orientifold projection we remain with $n_v^-$ $\caln=1$ vector multiplets and $n_h+n_v^+$ $\caln=1$ chiral multiplets. As is customary, we will continue to call the $\caln=1$ chiral multiplets which come from $\caln=2$ vector multiplets as vector multiplet moduli and those which come from $\caln=2$ hypermultiplets as hypermultiplet moduli.

Now it was shown in [@grilo], [@grimm] that after orientifold projection the Kähler potential for the hypermultiplets in the cubic region is of the form $$\eqlabel{gl} K = - \log(\tau-\bar\tau) - 2\log
\ee^{-3\phi/2}\kappa_{abc} v^av^bv^c,$$ where $v^a$ are some real coordinates on the hypermultiplet moduli space (Kähler moduli in type IIB) and $\kappa_{abc}$ are the Yukawa couplings. See in particular chapter 3, section 3 of [@grimm]. The main point of the discussion is that one should view the $v^a$ as the worldsheet couplings, whereas the holomorphic coordinates on the hypermultiplet moduli space from the spacetime point of view contain as real part the ${\rm Re}(T_a) \sim
\ee^{-\phi/2}v^a$, where $\ee^{-\phi}= {\rm 