  We discuss a scenario in which extra dimensional effects allow a scalar field
with a steep potential to play the dual role of the inflaton as well as dark
energy (quintessence). The post-inflationary evolution of the universe in this
scenario is generically characterised by a `kinetic regime' during which the
kinetic energy of the scalar field greatly exceeds its potential energy
resulting in a `stiff' equation of state for scalar field matter $P_\phi \simeq
\rho_\phi$. The kinetic regime precedes the radiation dominated epoch and
introduces an important new feature into the spectrum of relic gravity waves
created quantum mechanically during inflation. The gravity wave spectrum
increases with wavenumber for wavelengths shorter than the comoving horizon
scale at the commencement of the radiative regime. This `blue tilt' is a
generic feature of models with steep potentials and imposes strong constraints
on a class of inflationary braneworld models. Prospects for detection of the
gravity wave background by terrestrial and space-borne gravity wave
observatories such as LIGO II and LISA are discussed.
