  We investigate the evolution of gravitational wave perturbations about a
brane cosmology embedded in a five-dimensional anti-de Sitter bulk. During
slow-roll inflation in a Randall-Sundrum brane-world, the zero mode of the
5-dimensional graviton is generated, while the massive modes remain in their
vacuum state. When the zero mode re-enters the Hubble radius during radiation
domination, massive modes are generated. We show that modes decouple in the
low-energy/near-brane limit and develop perturbative techniques to calculate
the mode-mixing at finite energy.
