Cosmological bounds on large extra dimensions from nonthermal production of Kaluza-Klein modes

The existing cosmological constraints on theories with large extra dimensions rely on the thermal production of the Kaluza-Klein (KK) modes of gravitons and radions in the early Universe. Successful inflation and reheating, as well as baryogenesis, typically requires the existence of a TeV-scale field in the bulk, most notably the inflaton. The nonthermal production of KK modes with masses of order 100 GeV accompanying the inflaton decay sets the lower bounds on the fundamental scale M-*. For a 1-TeV inflaton, the late decay of these modes distorts the successful predictions of big bang nucleosynthesis unless M-*>35, 13, 7, 5, and 3 TeV for two, three, four, five, and six extra dimensions, respectively. This improves the existing bounds from cosmology on M-* for four, five, and six extra dimensions. Even more stringent bounds are derived for a heavier inflaton.