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

The existing cosmological constraints on theories with large extra dimensions rely on the thermal production of the Kaluza-Klein 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 non-thermal 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 distort the successful predictions of Big Bang Nucleosynthesis unless M∗ > 35, 13, 7, 5 and 3 TeV for 2, 3, 4, 5 and 6 extra dimensions, respectively. This improves the existing bounds from cosmology on M∗ for 4, 5 and 6 extra dimensions. Even more stringent bounds are derived for a heavier inflaton.