In recent years it has been realized that pre-BBN decays of moduli can be a significant source of dark matter production, giving a " nonthermal WIMP miracle" and substantially reduced fine-tuning in cosmological axion physics. We study moduli masses and sharpen the claim that moduli dominated the pre-BBN universe. We conjecture that in any string theory with stabilized moduli there will be at least one modulus field whose mass is of order (or less than) the gravitino mass. Cosmology then generically requires the gravitino mass not be less than about 30 TeV and the cosmological history of the universe is nonthermal prior to BBN. Stable LSP's produced in these decays can account for the observed dark matter if they are "wino-like." We briefly consider implications for the LHC, rare decays, and dark matter direct detection and point out that these results could prove challenging for models attempting to realize gauge mediation in string theory.
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We appreciate helpful conversations with Shanta de Alwis, Konstantin Bobkov, Frederik Denef, Michael Douglas, Daniel Feldman, Piyush Kumar, Aaron Pierce, and Fernando Quevedo. We would also like to thank C. Scrucca and J. Louis for pointing out an error in the previous version of this article. B. S. Acharya is grateful to the University of Michigan Physics Department and MCTP for support, and E. Kuflik is grateful to the String Vacuum Project for travel support and for a String Vacuum Project Graduate Fellowship funded through NSF grant PHY/0917807. This work was supported by the DOE Grant #DE-FG02-95ER40899.
- Dark matter
- String phenomenology