prepotential for vector multiplets is not renormalized [@Vafaaug]. One simple argument for this is that in $\caln=2$ supersymmetric theories neutral hypermultiplets and vector multiplets do not couple and the dilaton is part of a hypermultiplet. Furthermore, $\alpha'$ corrections can be excluded as they contain the size of the Calabi-Yau which is a Kähler modulus. Using the $SL(2,\zet)$ symmetry of the type IIB theory we can write down the unique $SL(2,\zet)$ invariant combination of the superpotential $$W=\int G \wedge \Omega,$$ where $G=H_{RR}-\tau H_{NS}$. The complete superpotential is then not renormalized as the $\caln=2$ prepotential is not corrected. This argument is already enough to ensure the existence of Minkowski vacua, which are solutions to the equation $\partial_i W=0$, where ‘$i$’ denotes the moduli. Some more thought is needed to guarantee the existence of supersymmetric AdS vacua which are solutions to the equation $D_iW=\partial_iW+\partial_iK W=0$. This is due to Kähler invariance [@BVW]. Namely suppose we can choose the coordinates for the moduli $t_i$ in such a way that the Kähler potential has an expansion $$K=t_i\bar t_i+a_{ij}t_i\bar t_j f(t,\bar t),$$ where $t_i=\bar t_i=0$ describes our solution. Quantum corrections to $\partial_iK$ evaluated at $t_i=\bar t_i=0$ will affect the solution only by terms which are purely 