The Friedmann Equation in Brane-World Scenarios

Justin Khoury, Ren-Jie Zhang
2002 Physical Review Letters  
The Friedmann law on the brane generically depends quadratically on the brane energy density and involves a "dark radiation" term due to the bulk Weyl tensor. Despite its unfamiliar form, we show how it can be derived from a standard four-dimensional Brans-Dicke theory at low energy. In particular, the dark radiation term is found to depend linearly on the brane energy densities. For any equation of state on the branes, the radion evolves such as to generate radiation-dominated cosmology. The
more » ... diation-dominated era is conventional and consistent with nucleosynthesis.
doi:10.1103/physrevlett.89.061302 pmid:12190574 fatcat:4v7xkjfsrnhejbtyzb2bh2i3he