Constraints on meta-stable de Sitter flux vacua

We consider flux compactification of type IIB string theory as the orientifold limit of an F-theory on a Calabi-Yau 4-fold. We show that when supersymmetry is dominantly broken by the axion-dilaton and the contributions of the F-terms associated with complex structure moduli are small, the Hessian of the flux potential always has tachyonic modes for de Sitter vacua. This implies that there exist no meta-stable de Sitter vacua in this limit. Moreover, we find that the stability requirement imposes a relation between the values of cosmological constant and the scale of supersymmetry-breaking for non-supersymmetric anti-de Sitter vacua in this limit. The proof is general and does not rely on the details of the geometry of the compact Calabi-Yau internal space. We finally analyze the consequences of these constraints on the statistics of metastable de Sitter vacua and address some other related issues.

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Published 1 January 2009