The radion in brane cosmology Original Research Article

We consider the homogeneous cosmological radion, which we define as the interbrane distance in a two-brane and Z2 symmetrical configuration. In a coordinate system where one of the brane is at rest, the junction conditions for the second (moving) brane give directly the (nonlinear) equations of motion for the radion. We analyse the radion fluctuations and solve the nonlinear dynamics in some simple cases of interest.