Strong constraint on large extra dimensions from cosmology
Abstract
We have studied cosmological constraints on the number and radii of possible large extra dimensions. If such dimensions exist, Kaluza-Klein (KK) modes are copiously produced at high temperatures in the early universe, and can potentially lead to unacceptable cosmological effects. We show that during reheating, large numbers of KK modes are produced. These modes are not diluted significantly by the entropy production during reheating because they are produced non-relativistically. If the maximum temperature of the universe during reheating is higher than a few MeV, the constraints on extra dimensions from this effect are much stronger than any other known astrophysical or laboratory limits. For example, for two compact extra dimensions the upper bound on the radii is R < 1.7 x 10^-7 mm if the highest temperature during reheating is 5 MeV.Keywords
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