The abstract of this paper is:
We study the properties of M and F theory compactifications to three and four
dimensions with background fluxes. We provide a simple construction of
supersymmetric vacua, including some with orientifold descriptions. These
vacua, which have warp factors, typically have fewer moduli than conventional
Calabi-Yau compactifications. The mechanism for anomaly cancellation in the
orientifold models involves background RR and NS fluxes. We consider in detail
an orientifold of
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Savdeep Sethi says on Distler's blog post : I spent a great deal of time studying and constructing the first F-theory compactifications with flux (hep-th/9908088), and I am not sanguine (although I am still thinking about it).