Type IIB Flux Vacua and Tadpole Cancellation

We consider flux vacua for type IIB orientifold compactifications and study their interplay with the tadpole-cancellation condition. As a concrete example we focus on T6/Z2xZ2, for which we find that solutions to the F-term equations at weak coupling, large complex structure and large volume require large flux contributions. Such contributions are however strongly disfavored by the tadpole-cancellation condition. We furthermore find that solutions which stabilize moduli in this perturbatively-controlled regime are only a very small fraction of all solutions, and that the space of solutions is not homogenous but shows characteristic void structures and vacua concentrated on submanifolds.